AN IMPROVED CHRONOMETER ESCAPEMENT
Year: 1875

page_text: LETTERS PATENT to Matthias Petersen, of Altona, Prussia, for the
Invention of " AN IMPROVED CHRONOMETER ESCAPEMENT."
PROVISIONAL SPECIFICATION left by the said Matthias Petersen at
the Office of the Commissioners of Patents, with his Petition, on
the 4th June 1875.
I, MATTHIAS PETERSEN, of Altona, Prussia, do hereby declare the
nature of the said Invention for "AN IMPROVED CHRONOMETER ESCAPEMENT,”
to be as follows:-
This Invention relates to an improved chronometer escapement, and
has for its object to make this mechanism simpler in design, more certain
in action, and less liable to derangement than heretofore.
The detent spring of the common chronometer escapement is dispensed
with, and in its place a cylinder of steel, the acting face of which may
be lined with a jewel, serves to lock the escape wheel. This cylinder,
oscillating on pivots, is maintained in the locking position by a spring.

page_text: The cylinder carrics a lever extending towards the balance; this lever
is actuated by another lever on the axis of the balance, or by a vertical
pin inserted into the impulse disc or into the arm of the balance. By
this action the unlocking of the escape wheel takes place; the cylinder
being turned to a certain amount a flattened part of the same allows the
hitherto locked tooth of the wheel to pass, another tooth at the same
time giving a new impulse to the balance in the usual manner. As
soon as the lever or pin of the balance has cleared the lever of the
cylinder the latter resumes the locking position by means of the aforesaid
spring. On the returning vibration of the balance the lever of the same
strikes the lever of the cylinder from the back, thereby causing the
cylinder to oscillate slightly in a direction contrary to the former, its
normal position being restored immediately after by means of the
spring.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Matthias Petersen in the Great Seal Patent Office
on the 3rd December 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MATTHIAS
PETERSEN, of Altona, Prussia, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourth day of June, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Matthias Petersen, Her special license that
I, the said Matthias Petersen, my executors, administrators, and assigns,
or such others as I, the said Matthias Petersen, my executors, admini-
strators, 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 "AN IMPROVED CHRONOMETER
ESCAPEMENT," upon the condition (amongst others) that I, the said
Matthias Petersen, 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

page_text: 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 Matthias Petersen, 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 thereof, that is to say :-
This Invention relates to an improved chronometer escapement, and
has for its object to make this mechanism simpler in design, more certain
in action, and less liable to derangement than heretofore.
The Invention will be clearly understood by reference to the annexed
Sheet of Drawings, in which A, A, is the escape wheel, and B, B, the
impulse disc of the ordinary detent escapement; C is the balance staff.
Instead of the detent spring hitherto used a locking cylinder is placed
near the circumference of the escape wheel, the teeth of which take
their rest or locking on its concentric surface. The cylinder D is capable
of a movement round its axis on two pivots. In corresponding height
with the escape wheel this cylinder is flattened down to its centre, and a
spring E by its action against this flattened part keeps it in its locking
position.
The lever F is fastened to the cylinder, and extends towards the
balance staff, which carries also a lever G in the same height; this latter
lever, when the balance is moving in the direction of the arrow, by
engaging the lever F operates a small rotary movement of the locking
cylinder D, so that the wheel tooth drops from its rest as soon as the
edge of the flattened cylinder has passed (Figure 1). Then the impulse
takes place in the ordinary way, and the locking cylinder returns to its
position of rest as soon as the unlocking lever G allows the lever F to
drop. In the returning vibration of the balance the lever G moves the
lever Fa little the other way, after which this latter immediately
resumes its normal position by the action of the spring E.
If applied to chronometers a slight modification of this before described
simplest form of my escapement will be advisable. The acting extremity
of the lever G.may be provided with a ruby (Figure 1), or the lever may
be replaced altogether by a ruby pin inserted vertically into a hole in
the impulse disc (Figure 2), or in the balance arm.

page_text: The locking part of the cylinder ought to be jewelled by inserting a
semi-cylinder of ruby into a hollow steel cylinder, which must be cut out
sufficiently for exposing the acting part of the ruby cylinder.
The leven F ought to have a prolongation beyond its centre of oscil-
lation, and to its end is fastened a small gold spring (Figure 3) like the
unlocking spring of the detent escapement. The spring E then may be
replaced by a hair spring fastened to the axis of the cylinder. This
arrangement requires a set screw for limiting the depth of locking.
The advantages of my escapement are,―
1. The unlocking resistance of the common detent escapement is
reduced to a very small sliding friction, because the wheel is locked by a
cylindrical surface and without any "draw," till now thought indis-
pensable for the safe performance of a detached escapement.
The cylinder with its lever is of very little weight, and can be
carefully equipoised, so that it is absolutely safe against any disturbance
by shocks, while the detent, which cannot be poised, must have a con-
siderable tension in order to maintain its locking function in all positions
of the chronometer; this tension occasions a loss of power at each
vibration of the balance. This loss in the German chronometer escape-
ment is reduced to the smallest amount possible without any prejudice
to the safety of action.
3. The unlocking lever G of the German chronometer escapement can
be made much longer than that of the detent escapement, and therefore
the unlocking angle may with the same safety of action be reduced to
less than half of what is necessary for the detent escapement. By this
considerable improvement of the weakest point of chronometer escape-
ments, the liability to "set," this new escapement shows a decided
superiority for portable chronometers.
4. The organs of this escapement are not so delicate and frail as those
of the detent escapement, and their adjustment is not dependent on that
degree of accuracy which the former requires, and thereby the excellent
timekeeping qualities of the chronometer escapement are brought within
the range of current manufacturing.
5. No necessity of oil at the locking surface.
6. Cheaper production of the escapement.
What I claim as new and of my Invention is,-
-

page_text: Firstly. The employment of a locking cylinder D forming a circular
rest without any recoil of the wheel in unlocking, as shown and
described.
Secondly. The levers G and F of handy dimensions, allowing of
accurate adjustment and utmost reduction of the unlocking angle, as
shown and described.
Thirdly. The spring E for bringing the cylinder back to its normal
position, or a hair spring for the same purpose, as shown and described.
Fourthly. The application of rubies to or instead of the lever G, and
to the locking cylinder D, substantially as shown and described.
And, Fifthly. The combination of mechanism and parts thereof,
substantially as shown and described when used for the purposes set
forth.
In witness whercof, I, the said Matthias Petersen, have hereunto
set my hand and seal, this Twenty-ninth day November, One.
thousand eight hundred and seventy-five.
MATTHIAS PETERSEN. (L.S.)