IMPROVEMENTS IN COMPENSATION BALANCES FOR MARINE AND OTHER CHRONOMETERS
Year: 1876

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS IN
COMPENSATION BALANCES FOR MARINE AND OTHER CHRONOMETERS." A com-
munication froin abroad by Joseph Thadocus Winnerl, of Paris, France.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 10th March 1876.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
IMPROVEMENTS IN COMPENSATION BALANCES FOR MARINE AND
OTHER CHRONOMETERS."
In order to render the rate of a chronometer independent of the influence which
a change of temperature exerts on the balance wheel and spring, it has been usual
to employ a compensating balance consisting principally of arcs or circular arms
composed of two different metals. In order to correct the error to which a chro-
nometer adjusted to go without any sensible variation at a medium temperature is
still liable when the temperature rises or falls, various contrivances have been added
to increase the effect produced by a rise of temperature and to moderate the effect
of a fall in temperature, but they are for the most part complicated and of great
delicacy and involve a great amount of work and expenditure of time in making
the necessary tests, it being necessary to dismount the balance wheel every time
they are adjusted.
The object of this Invention is to produce a compensation balance of simple
construction, capable of being easily regulated for different temperatures without being
dismounted, and having a perfectly isochronal balance spring.
The Invention consists essentially, 1st, in the exclusive employment of flat
straight compound arms; 2nd in the combination with theso anus of screws inclined
at an angle of about 45 degrees to the horizontal plane of said arms and carrying
adjustable weights screwing therein; 3rd, in regulating the compensation for
different temperatures by varying the inclination of the said screws, and by
adjusting the weights at different positions of their length.
In order that the Invention may be more readily understood, I have illustrated
in the annexed Drawing an example of the improved compensation balance, which
may, however, be considerably modified, according to the different conditions under
[Price 6d1

page_text: which it is applied as regards the available space in the chronometer, the balance
shown being suited for a chronometer of a particular size. Figures 1 and 2 respec-
tively represent an elevation and plan of the improved compensation balance, and
Figure 3 shows a side elevation of the crossbar carrying the timing screws.
Figure 4 illustrates diagrammatically the principle of action of the improved
balance. The same letters of reference indicate the same parts in Figures 1, 2, 3.
A is the arbor of the balance, and B, B, a crossbar fixed thereto. C, C, is another
crossbar composed of a single metal fixed to bar B by screws or otherwise.
D, D, timing screws or nuts of platinum or other metal screwing on screw pins fixed
at the ends of bar C. The bar Bterminates in return pieces E, E, to which are fixed
the two plane straight compound arms F and G, made of steel and brass (or equiva-
lent combination of metals) the steel being above and the brass below. The free
extremities of the arms are bent up as shown, and to then screws H are fixed at an
angle from the horizontal plane of the arms of about 45°. P, P, are nuts or compen-
sating weights made of platinum or other metal screwing on H. They are of the
form shown or other synimetrical form, and are notched as at K to receive a turn-
screw. The diagram Figure 4 illustrates the compensating action of the balance. The
compound arms F, G, are straight at the medium temperature, say 15° cent., but if
the temperature rise, say 30° cent., each arm will curve upwards. The screw H
is thereby raised, and, moreover, as the angle which it makes with the last element
of the compound arm is invariable, it follows that it will incline still further from
the horizontal plane to an angular extent equal to the angular movement of the
said element, that is to say, equal to the change of curvature of the arm. If, on the
other hand, the temperature falls from the medium temperature of 15° c. to, say
zero, the arms curve in the opposite direction to an equal extent and assume the
lowest position, A, B, M, Figure 4. It will be readily seen by inspection of the
Drawing that the effect (which is confirmed by calculation) is to increase the move-
ment of the weight carried by the screw towards the axis upon the rise of tem-
perature, and to decrease the movement away from the centre upon the fall of
temperature. This is precisely the result sought to be attained by secondary
compensation. It will be readily seen with what facility the regulation may be
effected. Suppose the screws H to have been placed at an angle of 45° from the
horizontal. In order to obtain an equal rate at the two extremes of temperature,
it is only necessary to adjust the two compensation weights along their screws.
The equality of rate at the two extreme temperatures having been attained, if the
chronometer gains slightly at the intermediate temperatures, it is only necessary
to reduce the inclination of the screw stems from the horizontal to 42° or 40° for
example. If on the other hand the chronometer loses at the intermediate tem-
peratures this inclination must be slightly increased.
This trial for the proper
inclination of the screw stems requires to be made once only, for a number of
chronometers of similar construction and the proper inclination for a particular form
of balance and spring being once found, the regulation is effected by adjusting the
compensation weights along the screws. This adjustment being along a screw may
be made within the narrowest possible limits without dismounting the balance, in
the same way that the rate is regulated by the timing screws. If the depth of
space available will admit, the compound arms may be placed above the crossbar,
whereby the said arms may be brought nearer to the arbor of the balance; in this
case the compound arms must be placed above the cross bar at a suitable distance
to facilitate their action at different temperatures, which tends to raise the two
extremities of the bar on which the compound arms are fixed. If the available
space is too small in diameter the arms can no longer afford sufficient composition,
or the compensation weights may require to be excessively raised to produce the
necessary effect. In this case the two portions of the crossbar B, comprised between
the arbor socket and the return pieces É may be compound, the upper part brass, and
the lower part steel.

page_text: 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 9th
September 1876.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex
Patent Agent.
"IMPROVEMENTS IN COMPENSATION BALANCES FOR MARINE AND
OTHER CHRONOMETERS." A communication from abroad by Joseph Thadous
Winnerl, of Paris, France.
In order to render the rate of a chronometer independent of the influence which
a change of temperature exerts on the balance wheel and spring, it has been usual
to employ a compensating balance consisting principally of arcs or circular arms
composed of two different metals. It has, however, been found by experience
impossible to obtain perfect compensation for the various changes of temperature
with this description of balance. If a balanco of this kind be employed with a
perfectly isochronal spring, it is possible by a suitable adjustment of the weights
upon the wheel to obtain the same rate at two fixed temperatures, at 32° and 86°
Fabr. for example, but the rate will not remain the same at intermediate tempera-
tures, at about 59° for instance there will be a greater or less gain, which under
the most favorable circumstances will not be less than two seconds per day. In
other words, if the chronometer at a temperature of from 32° to 86° beats exactly
86,400 seconds per day, it will beat 86,402 seconds at 59°. If the chronometer be
so regulated as to go at the same rate at 59° and 86° the error then occurs at low
temperatures, and there is generally a loss of 4 seconds at a temperature of 32°. It
has been proposed to obtain an apparently inore accurate compensation by employing
instead of an isochronal spring one which will gain 4 seconds when the amplitude
of the arcs is reduced by a temperature of 32°, so that the gain due to the spiral will
compensate for the loss due to the balance. This method is, however, defective, and
imports into the chronometer an element of variation in the rate subject to the
influence of increased resistance and diminution of power resulting from the thickening
of the oil, the wear of the pivots, &c.
It has also been sought to obtain a more perfect compensation for variations of
temperature and yet retain the advantages of synchronism. Suppose the rate of the
chronometer in question to be accurate at a medium temperature of 59° at 32° it will
lose two seconds per day, at 86° it will also lose two seconds per day. From this
it is evident that the compensating weights are not brought sufficiently near the
centre as the temperature rises above the medium, and are removed too far from it
when the temperature falls below the medium. To remedy this, various contrivances
terined secondary compensations have been added to increase the effect produced
by a rise of temperature, and to moderate the effect of a fall of temperature, but they
are for the most part complicated and of great delicacy, and involve a great amount
of work and expenditure of time in making the necessary tests, it being necessary to
dismount the balance wheel every time they are adjusted.
The object of this Invention is to produce a compensation balance of a simple
construction capable of being easily regulated for different temperatures without
being dismounted, and having a perfectly isochronal balance spring.
The Invention consists essentially, 1st, in the exclusive employment of flat
straight compound arms; 2nd, in the combination with these arms of screws inclined
at an angle of about 45 degrees to the horizontal plane of said arms and carrying
adjustable weights screwing like nuts thereon; 3rd, in regulating the compensation
for different temperatures by varying the inclination of the said screws, and by
adjusting the weights at different positions of their length.
In order that the Invention may be more readily understood, I have illustrated
in the annexed Drawing an example of the improved compensation balance, which
may, however, be considerably modified, according to the different conditions under
which it is applied as regards the available space in the chronometer, the balance
shown being suited for a chronometer of a particular size.
Figures 1 and 2 respectively represent an elevation and plan of the improved

page_text: compensation balance, and Figure 3 shows a side elevation of the crossbar carrying
the timing screws. Figure 4 illustrates diagrammatically the principle of action of
the improved balance. The same letters of reference indicate the same parts in
Figures 1, 2, 3.
A is the arbor of the balance, and B, B, a crossbar of steel or other metal fixed
thereto; C, C, is another crossbar composed of a single metal fixed to bar B by
screws or otherwise; D, D, timing screws or nuts of platinum or other metal screwing
on screw pins fixed at the ends of bar C. The bar B terminates in return pieces E, E,
to which are fixed the two plane straight compound or bi-metallic armis F and G,
made of steel and brass, zinc and platinum (or equivalent combination of metals),
the steel being above and the brass below. The free extremities of the arms are
bent as shown, and to them screws H are fixed at an angle from the horizontal
plane of the arms of about 45°. P, P, are nuts or compensating weights made of
platinum or other inctal screwing on H. They are of the form shown or other symme-
trical form, and are notched as at K to receive a turnscrew. The diagram Figure 4
illustrates the compensating action of the balance. The compound arms F, G, are
straight at the medium temperature, say 50°, but if the temperature rise to say 86°,
each arm will curve upwards. The screw H is thereby raised, and, moreover, as
the angle which it makes with the last element of the compound arm is invariable,
it follows that it will incline still further from the horizontal plane to an angular
extent equal to the angular movement of the said element, that is to say, equal to
the change of curvature of the arm. If on the other hand the temperature falls
from the medium temperature of 59° to say 32°, the arms curve in the opposite
direction to an equal extent, and assume the lowest position A, B, M, Figure 4.
It will be readily seen by inspection of the Drawing that the effect (which is
confirmed by calculation) is to increase the movement of the weight carried by the
screw towards the axis upon the rise of temperature, and to decrease the movement
away from the centre upon the fall of temperature. This is precisely the result
sought to be attained by secondary compensation. It will be readily seen with
what facility the regulation may be effected. Suppose the screws H to have been
placed at an angle of 45° from the horizontal. In order to obtain an equal rate at
the two extremes of temperature it is only necessary to adjust the two compensation
weights along their screws. The equality of rate at the two extreme temperatures
having been obtained, if the chronometer gains slightly at intermediate temperatures,
it is only necessary to reduce the inclination of the screw stems from the horizontal
to 42° or 40° for example. If on the other hand the chronometer loses at the
intermediate temperatures this inclination must be slightly increased. This trial
for the proper inclination of the screw stems requires to be made once only for a
number of chronometers of similar construction, and the proper inclination for a
particular form of balance and spring being once found, the regulation is effected
by adjusting the compensation weights along the screws. This adjustment being
along a screw may be made within the narrowest possible limits without dismounting
the balance in the same way that the rate is regulated by the timing screws.
If the depth of space available will admit, the compound arms may be placed
above the crossbar, whereby they may be brought nearer to the arbor of the
balance in this case the arms must be placed above the crossbar at a suitable
distance to facilitate their action at different temperatures, which tends to raise the
two extremities of the bar on which the compound arms are fixed. If the available
space is too small in diameter the arms can no longer afford sufficient compensation,
or the compensation weights may require to be successively raised to produce the
necessary effect.
In this case the two portions of the crossbar B comprised between
the arbor socket and the return pieces E may be compound, the upper part brass
and the lower part steel.
Having described the nature of the said Invention, and the manner of performing
the same,
I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is-
Constructing compensating balances with flat straight compound arms, having fixed

page_text: at their free ends (at an inclination of about 45°) screw pins with weights screwing
therein, as herein shown and described, the whole with the object of enabling the
regulation for different temperatures to be effected by slightly varying the
inclination of the screw pins and adjusting the position of the weights thereon.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Ninth day of September, in the year of our Lord One
thousand eight hundred and seventy-six.
L
CIT
DI
L
A. M. CLARK. (L.S.)