IMPROVEMENTS IN EQUI-MOTIVE ESCAPEMENTS FOR WATCHES, CLOCKS, AND OTHER TIME- KEEPERS
Year: 1877

page_text: LETTERS PATENT to Harrison Mill Frodsham, of the Strand, in the County of
Middlesex, Chronometer Maker, for the Invention of "IMPROVEMENTS IN
EQUI-MOTIVE ESCAPEMENTS FOR WATCHES, CLOCKS, AND OTHER TIME-
KEEPERS."
ealed the 13th July 1877, and dated the 15th January 1877.
PROVISIONAL SPECIFICATION left by the said Harrison Mill Frodsham at
the Office of the Commissioners of Patents on the 15th January 1877.
HARRISON MILL FRODSHAM, of the Strand, in the County of Middlesex, Chro-
nometer Maker. "IMPROVEMENTS IN EQUI-MOTIVE ESCAPEMENTS FOR WATCHES,
CLOCKS, AND OTHER TIMEKEEPERS."
This Invention relates to improvements in independent equi-motive escapements
for watches, clocks, and other timekeepers.
According to my Invention the impulse given to the balance or pendulum is
always of equal force, and the resistance to be overcome by the balance or penduluin
in unlocking the impulse lever is also always the same.
Instead of communicating the force of the train by means of any of the ordinary
escapements directly to the balance or pendulum, the scape pallets are employed to
tense a spring (or springs) always to the same extent. This spring (or springs)
which by means of a lever (or levers) impels the balance, is when tensed, locked in
position, and as it is always tensed to the same degree, it will, on being unlocked by
the balance or pendulum, communicate to it a constant impulse.
One method of carrying out my Invention as applied to a balance is as follows:-
Fixed to the pallets working on to the scape wheel is one end of a blade or wire
spring, the other end of which is provided with a pin working in a slot made for
that purpose in a lever called the impulse lever which is attached to an arbour
working in suitable bearings. The motion of the scape wheel and pallets is com-
municated to and so tenses the said spring. The spring through its tension imparts
motion to the inpulse lever, and the impulse lever gives the impulse to the balance
in the ordinary manner, namely, through the medium of the impulse pin on the
balance roller. After giving the impulse the lever is locked, and remains so whilst
the spring is being tensed to give the reverse impulse.
The method of locking is as follows:-As the lever is completing its beat to one
Duis

page_text: At the
side and just before the impulse pin (having received the impulse) quits it, a pin
near the extremity of the lever comes in contact with the head of its spring
detent and raises it sufficiently to allow the impulse pin to pass which it does by
reason of the momentum of the balance. Or the impulse pin or a projection on the
roller in passing may be made to raise or assist in raising the said detent.
instant of the impulse pin passing the detent and leaving the lever, a projection or
arm on the latter comes in contact with a detent locking the driving train and
unlocks it, and at the same moment the pin in the impulse lever slips under the
head of its detent which springs down and locks the lever at the extremity of its
beat. The train being unlocked causes the scape wheel to advance a tooth and is
then again locked by its own detent. This motion of the scape wheel being com-
municated to the pallets tenses the spring in the direction for the opposite impulse,
and thus at each escape of the train the spring is tensed alternately in opposite
directions, and whilst the balance is out of connection with it, to an extent which is
constant. The impulse pin on its return or recoil vibration comes in contact with
the head of the detent locking up the impulse lever, raising same, releasing the
impulse lever and at the same time entering the notch in the end thereof and
receiving the next impulse. The impulse lever being thus released is forced over to
the other side by the tension of its spring, where, after raising the head of its detent
on that side, and allowing the pin on the balance roller to pass, it unlocks the train
as before described, and is then itself locked up by its detent, the head of which
slips down ready to be acted upon by the impulse pin on its return vibration, as
before described. Any other well known form of lever escapement, such as the two
pin lever or solid impulse lever, may be employed for communicating the force due
to the tension of the spring to the balance roller, the lever being locked up as
described or on rollers before the delivery of the impulse. Or the lever may at its
extremity take the form of a segment of a duplex escape wheel with one locking
and two impulse teeth, the latter both facing the centre of the lever. The lever is
actuated by the tension of a spring as before described, but as in the case of the
duplex escapement, the locking tooth rests on a roller on the balance staff until
released by the notch in the roller, allowing the point of the tooth to escape when
the impulse is given to the balance by one of the impulse teeth as in the duplex
escapement. The lever at the close of its beat unlocks the train, and is then
brought back again by the opposite tension of the spring to rest upon the roller
until released as before to give the impulse in the opposite direction.
A modified way of carrying out my Invention is to cause the lever impulsed by
the spring, instead of imparting motion to the balance as before described, to act
upon the faces of a pair of ordinary anchor pallets, the extremity of the said lever
being formed as a segment of an ordinary scape wheel, having but two teeth on it
pointing in opposite directions. These teeth receiving the constant impulses of the
spring in alternate directions act upon the faces of the pallets and lock themselves
thereon as in the ordinary action of the pallets and scape wheel. The pallets
through the medium of any well known form of lever impel the balance in the
ordinary manner.
Two springs actuating each a lever may also be tensed by suitable pallets work-
ing on the scape wheel, the levers being locked whilst the springs are tensed. They
are so arranged that one lever impels the balance or pendulum in one direction, and
the other in the opposite, each remaining locked until released by the vibration of
the roller or pendulum, and at the conclusion of its beat unlocking the train to tense
the opposite spring.
Instead of employing detents or rollers to lock the train, the same may be
locked upon or by the impulse lever being released by the latter as it nears the
extremity of its beat in either direction. Weights may be used instead of springs.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Harrison Mill Frodsham in tlie Great Seal Patent Office on the 14th
July 1877.
HARRISON MILL FRODSHAM, of the Strand, in the County of Middlesex, Chro-
nometer Maker. "IMPROVEMENTS IN EQUI-MOTIVE ESCAPEMENTS FOR WATCHES,
CLOCKS, AND OTHER TIMEKEEPERS."
"
This Invention relates to improvements in independent equi-motive escapements
for watches, clocks, and other timekeepers.
According to my Invention an impulse is given to the balance or pendulum at
each vibration of same, that is, at each escape of the train; the impulse given is
always of equal force, and the resistance to be overcome by the balance or pendulum
is likewise always the same. Thus each vibration or beat of the balance or
pendulum occupies precisely the same time, and the result is a perfect timekeeper.
According to my Invention the motive force is not communicated directly to the
balance or pendulum as is the case with escapements ordinarily used, but instead is
governed and directed as follows:-It is made to tense a spring (or springs) at each
escape of the train always to the same extent, and alternately in opposite directions
in order to give an impulse at each vibration of the balance or pendulum. This
spring (or springs) which either itself or through the medium of a lever (or levers)
gives the impulse to the balance or pendulum is before each occasion of being
tensed locked up at a given point and remains so while tensed, and until liberated
to give the impulse. It is always tensed to the same extent before giving the
impulse and will therefore communicate impulses of a constant force. The spring
or the impulsing lever actuated by it on completing the impulse to the balance or
pendulum reaches the point at which it is locked up as described. It then goes on
a little further, and whilst the balance or pendulum is entirely out of connection
with it, unlocks the train, thus allowing the scape wheel to advance and so tense
the spring (while locked up) ready to give the next impulse.
And in order that my Invention may be clearly understood and readily carried
into effect, I will proceed to describe it with the aid of the accompanying Drawings,
reference being had to the letters and figures marked thereon; like letters indicato
like parts.
Figures 1 and 2 illustrate on an enlarged scale my Invention in a simple form as
applied to a balance, Figure 1 being a front or face view, and Figure 2 a side or
edge view. Fixed to the pallets A, A, working into the scape wheel B is one end
of a blade spring C, the other end of which is provided with a pin c working in a
slot d made for that purpose in a lever D called the impulse lever, which is attached
to an arbour d' working in suitable bearings. In this case the arbour is shewn
working through that of pallets A, A. The action of the scape wheel B on the
pallets A, A, is communicated to and so tenses the spring C. The spring through
its tension imparts motion to the impulse lever D, and this gives the impulse to the
balance in the ordinary way, namely, through the medium of a pin e on the balance
roller E. As the lever D in giving the impulse completes its motion to one side,
and just before the impulse pin e (having received the impulse) leaves it, a pin d²
near the extremity of the lever comes in contact with the head of the lever's spring
detent F and depresses it sufficiently to pass, and also to allow the impulse pin e to
clear the projection f in its forward motion from the impulse imparted to it. Or
the impulse pin may be made to clear its own road by striking the projection f, and
so depressing the spring F. Or the impulse pin e, and the pin d², may be made to
strike simultaneously, and so conjointly depress the spring F. If desired also a
projection on the roller may take the place of the impulse pin as described for the
depression of the spring detent. The impulse pin having passed projection f, and
pin d having passed over the head of the detent F, the latter springs back but the
impulse lever D goes on a shade further, till a projecting arm d³, coming in contact
with a spring detent G locking the train, depresses same, unlocking the train, and

page_text: allowing the scape wheel B to advance till stopped by a detent G on the opposite
side. The motion of the scape wheel is communicated to the pallets A, A, and
thence to spring C, which is thus tensed for the next or opposite impulse by reason
of the impulse lever being locked behind the head of the spring detent G over
which it has passed, and which has sprung back behind it. Thus at each escape of
the train the spring is tensed, and alternately in opposite directions (and whilst the
balance is out of connection with it) to an extent which is always equal or constant.
Whilst the tensing of the spring has been effected, the balance has been continuing
its vibration. In its return vibration the impulse pin e on the balance roller E
comes in contact with projection f on spring detent F, and depresses same, releasing
the impulse lever, and at the same time entering the notch in the extremity thereof.
The impulse lever being thus unlocked is impelled over to the other side by the
tension of spring C, thus giving the next impulse to the balance, and in the reverse
direction to the last. As the impulse lever D completes its motion to this side the
way is cleared for the impulse pin, the lever is locked, and the train liberated, as
already described on the other side, and in fact the motions are repeated, and so on
at each escape of the train.
Figures 3 and 4 of the accompanying Drawings illustrate a modification of
application of my Invention, the locking of the impulse lever being simplified and
that of the train lightened. In other respects the form of application is similar to
that already described. Figure 3 is a front or face view, and Figure 4 a side or
edge view. In this case the scape wheel B has the scape teeth on its face, whilst
its periphery is provided with teeth gearing into a pinion H, on the spindle of
which is a fly and a three-tooth scape wheel I on which the locking of the train is
effected after each escape by spring detents G at the points g, g'. The unlocking of
the train is effected by a short arm d attached to the impulse lever D and working
between the extremities of the detents G, G', striking them alternately as the
impulse is impelled from one side to the other. The locking of the impulse lever is
effected on one detent F instead of on two, as shewn in the first form of my
Invention. For this purpose the extremity of the impulse lever is provided with
two horns d³, d, curved to avoid the staff of the balance, and extending to the rear
of same, the ends of these horns are so formed that by acting (alternately on two
semicircular pins F, F1, the spring detent is depressed, allowing the horn to pass
when the detent springs back and so locks the impulse lever. The unlocking of the
lever is effected by a projection K on balance staff coming in contact with the head
of the detent F, which is properly formed for that purpose as shewn. This pro-
jection K is so placed that it will effect the unlocking of the impulse lever at the
proper moment, viz., just when the impulse pin on the return vibration of the
balance is entering the notch in the head of the impulse lever to receive the next
impulse.
With the above forms of applying my Invention the pallets have no locking
planes. There may however be employed with advantage a short dead surface at
the extremity of each pallet plane so as to prevent the tense spring backing the
train. Any other well known form of lever escapement such as the two-pin lever
or solid impulse lever may be employed for communicating the force of the tensed
spring to the balance, the lever being locked up as already described before the
tensing and the delivery of the impulse. Or the lever may at its extremity take
the form of a duplex scape wheel with one locking and two impulse teeth, the latter
both facing the centre line of the lever. The lever is actuated by the tension of a
spring as before described, but as in the case of, the duplex escapement, the locking
tooth rests on a roller on the balance staff until released by the notch in the roller,
allowing the point of the tooth to escape or pass the centre line, then the impulse is
given to the balance by one of the impulse teeth as in the duplex escapement. The
lever at the close of its beat unlocks the train, as before described, and is then
brought back again by the opposite tension of the spring to rest upon the roller
until released as before described to give the impulse in the opposite direction.
A modified way of carrying out my Invention is to cause the lever impulsed by

page_text: the spring (instead of imparting motion to the balance, as before described) to act
upon the faces of a pair of similar pallets, the extremity of the said lever being
formed as a segment of an ordinary scape wheel, having but two teeth pointing in
opposite directions. These teeth receiving the constant impulses of the spring in
alternate directions, act upon the faces of the pallets and lock themselves thereon as
in the ordinary action of the pallets and scape wheel. The pallets through the
medium of any well known form of lever impel the balance in the ordinary manner.
This form of my Invention is illustrated at Figures 5 and 6 of the accompanying
Drawings, Figure 5 being a front or face view, and Figure 6 a side or edge view.
L is the lever actuated by the tensed spring C, the teeth 1, 1, on the extremity of
which lever act upon the faces of a pair of pallets M, M, similar to pallets A, A.
These teeth 1, l, receiving the constant impulses of spring C in alternate directions
act upon the faces of pallets M, M, and lock themselves thereon as in the ordinary
action of the pallets and scape wheel. The pallets M, M, through the medium of
any well known form of lever D impels the balance in the ordinary manner.
In another form of application of my Invention instead of the spring C actuating
a lever to give the impulses to the balance, the spring may be made to act as the
lever itself to give the impulses. This form of my Invention is illustrated at
Figures 7 and 8 of the accompanying Drawings, Figure 7 being a front or face
view, and Figure 8 a side or edge view. C is the spring which is made also to
formn the impulse lever, as shewn. The locking of the train and of the lever, as will
be seen, is effected in a manner similar to that described under the second form of
application of my Invention.
Figures 9 and 10 indicate another way of locking the impulse lever, Figure 9
being a front or face view, and Figure 10 a side or edge view. The outer end of
impulse lever D is provided with two horns which are locked up alternately by
pallets N, N, the pallets being actuated by a pin O on the opposite face of the
balance roller to that on which the impulse pin is fixed. This pin O comes in
contact with lever P attached to pallets N, N, during the vibration of the balance,
thus impelling the lever and the pallets alternately from side to side, and so
alternately locking and liberating the impulse lever.
Figures 11 and 12 of the accompanying Drawings illustrate my Invention as
applied to an escapement for a pendulum, Figure 11 being a front or face view, and
Figure 12 a side or edge view. The spring C actuates a lever D in a slot, in which
works the impulse pin e attached to the pendulum at a point suitable to give the
required arc. The locking of the train is effected by spring detents G in a manner
similar to that already described. As the upper extremity of lever D completes its
motion to one side, the impulse pin e leaves it and it is locked in position by spring
detent F, and at the same time the lower extremity of lever D comes in contact
with detent G, locking the train, and liberates the train, to tense the spring C in the
reverse direction to give the next impulse. The impulse pin e now returns, and
striking the head of detent F depresses same, releases the impulse lever D, and
allows the next impulse to be given. The same actions take place on the other
side and so on alternately. The details of this arrangement are evident from the
illustrations. For pendulums it is evident weight detents may be used instead of
spring detents, and weights instead of the remontoir spring.
Instead of having only one spring tensed by the pallets, as herein-before
described, two springs actuating each a lever may be employed tensed by suitable
pallets working on the scape wheel to actuate two levers, the levers being locked
whilst the springs are being tensed. The levers are so arranged that one impels the
balance in one direction, and one in the opposite direction, and each remaining
locked until released by the vibration of the balance or pendulum, and at the con-
clusion of its beat unlocking the train to tense next the other spring. The details
necessary for such an arrangement as this are obvious from the descriptions of the
Invention already given, but this is not a form of my Invention that I recommend.
It will be obvious that my Invention may be carried out in other forms than
those shewn. For example, a coil spring may be used instead of a blade or wire

page_text: spring, and various modifications in the methods of locking and unlocking the train
and impulse levers may be employed.
Having thus particularly described and ascertained the nature of my said
Invention, and the manner in which the same is to or may be performed, I claim as
my Invention to be secured by the herein-before in part recited Letters Patent,
constructing escapements for watches, clocks, and other timekeepers, so that the
motive force is not communicated directly to the balance or pendulum, but is made
to tense a spring alternately to opposite sides, while the balance or pendulum is out
of connection with it, such spring being locked up before being tensed, and tensed
always to the same extent, and when tensed, being liberated by the balance or
pendulum to give same the next impulse, and so always delivering an impulse of a
constant force, and also so that the said spring or the impulse lever actuated by it
at the extremity of its motion, and after giving the impulse and whilst the balance
or pendulum is out of connection with it, unlocks the train to tense the spring in
the opposite direction for the next impulse.
In witness whereof, I, the said Harrison Mill Frodsham, have hereunto set
my hand and seal, this Thirteenth day of July, in the year of our Lord
One thousand eight hundred and seventy-seven.
HARRISON M. FRODSHAM. (L.S.)
Witness,
JOHN WM, GRAY, C.E.,
Patent Agent,
16, Southampton Buildings,
W.C.