IMPROVEMENTS IN INDEPENDENT EQUI-MOTIVE ESCAPEMENTS FOR WATCHES, CLOCKS, AND OTHER TIME-KEEPERS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Harrison Mill Frodsham- at the Office
of the Commissioners of Patents on the 15th July 1876.
HARRISON MILL FRODSHAM, of the Strand, in the County of Middlesex, Chrono-
meter Maker. "IMPROVEMENTS IN INDEPENDENT EQUI-MOTIVE ESCAPEMENTS FOR
WATCHES, CLOCKS, AND OTHER TIME-KEEPERS."
This Invention relates to improvements in independent equi-motive escapements
for watches, clocks, and other time-keepers.
According to my Invention the impulse given to the balance or pendulum is
always of equal force, and the weight or resistance to be overcome by the balance
or pendulum to effect the unlocking of the train is also always equal.
The impulse is given by a lever (called the impulse lever) actuated by a tensed
spring, the spring being tensed to an equal degree for each impulse, and so rendering
the force of the impulse a constant quantity. The impulse lever at the moment of
completing the impulse to the balance or pendulum in one direction ceases to be in
connection therewith, goes on a little further and unlocks the train, and is then
itself locked and remains so whilst its spring is being tensed to give the impulse
in the opposite direction. The balance or pendulum on its return vibration unlocks
this lever, which in its turn (and after the balance or pendulum has ceased to bo
in connection with it) unlocks the train. The force or resistance to be overcome
by the balance or pendulum to effect the unlocking of the train is thus also rendered
always equal.
A simple method of carrying out my Invention as applied to a balance is as
follows: To the arbor of the impulse lever the pallets working into the 'scape
wheel are attached so as to work freely thereon, and fixed to the pallets is one
end of a small blade or wire spring, the other end of which is provided with a
pin to work in a slot in the impulse lever, the spring thus taking (conveniently)
the centre line of the impulse lever. The motion of the pallets is communicated to
and so tenses the said spring. The spring, through its tension, imparts motion to the
impulse lever, and the lever gives the impulse to the balance in the ordinary manner,
namely, through the medium of the impulse pin on the balance roller. The lever
is locked after giving each impulse, and remains so whilst the spring is being tensed
to give the reverse impulse. As the lever is completing its beat to one side, and
just before the impulse pin has left it, and so got ahead, a pin near the extremity
of the impulse lever comes in contact with the head of a spring detent, and depresses

page_text: it sufficiently to allow the impulse pin to pass it, which it does by reason of the
momentum of the balance. Or the impulse pin in passing may be made to assist
in depressing the said detent. At the instant of the impulse pin passing the detent
and leaving the impulse lever the latter comes in contact with the detent of the
'scape wheel on that side and 'liberates the train, and at the same moment the pin
in the impulse lever slips over the head of the detent, which springs up and locks
the lever at the extremity of its beat. The 'scape wheel now advances a tooth, giving
motion to its pallets and tensing the spring of the impulse lever in the direction
for the opposite impulse, from which it will be seen that this spring is tensed at
each escape of the train alternately in the opposite directions and whilst the
balance is out of connection with it to an extent which is constant.
The impulse
pin on the balance roller now on its return vibration comes in contract with the
head of the detent of the impulse lever, depresses same, releases the lever, and
enters the notch in the end of the lever ready for the next impulse. The impulse
lever, now released, is forced over to the other side by the tension of its spring,
where after depressing the head of a detent on that side (similar to the one
described) and allowing the impulse pin to pass it comes in contact with and
releases the detent of 'scape wheel on that side, and is then itself locked by its
detent, the head of which slips up ready to be acted on by the impulse pin on its
return vibration. Thus the actions are carried on alternately on each side.
Weights may be used instead of springs.
Refinements and modifications of motion may be introduced.