IMPROVEMENTS IN LEVER ESCAPEMENT MECHANISM."
Year: 1874

page_text: LETTERS PATENT to William George Schoof, of Clerkenwell, in the
County of Middlesex, for the Invention of "IMPROVEMENTS IN LEVER
ESCAPEMENT MECHANISM."
Sealed the 4th August 1874, and dated the 10th April 1874.

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:
NOW KNOW YE, that I, the said William George Schoof, do hereby
declare that the following Complete Specification under my hand and
seal fully describes and ascertains the nature of the said Invention, and
in what manner the same is to be performed in and by the following
statement, reference being had to the accompanying Drawings, and to
the letters of reference marked thereon, that is to say :-
.
The objects of my Invention, more particularly as regards pocket
watches and marine chronometers, are to produce almost a separation
between the unlocking action and the impulse action, to do away
with the banking error, to prevent the pivots of the balance and the
ruby pin of the roller from injury by the "banking," which occurs
in ordinary lever watches through excessive vibration of the balance,
occasioned by violent external motion imparted to them, and to give
more security to the safety action, thereby rendering a double roller
unnecessary.
Instead of having the notch cut in the edge of the roller, and a
single pin or jewel in the lever acting on each side of the notch
alternately, I place a jewel or other pallet in the middle of a small
crescent cut out of the edge of the roller, and this pallet assists in
performing the last part of the unlocking action by engaging with
two upright pins or pallets fixed on the lever which act both as impulse
and guard pins. This arrangement does away with any possibility of
abutting, and allows the unlocking action to be performed by a ruby
pin put very near the centre of the roller, whereby an easier unlocking
is obtained.
According to another arrangement I make the. crescent pallet
perform the unlocking without any ruby pin in the roller, the only
other difference between this arrangement and the one just described
being that the crescent pallet has to be made a little longer. I thus
do away with the prongs and horns usually given to the lever, as the
two upright pins embrace the crescent pallet far enough to secure the
safety action.
My improvements in that part of the lever escapement called the
wheel and pallet action are as follows:-The wheel is placed between
the pallet and balance staff, whereby the pressure on the pallet pivots
is lessened as the force is transmitted on the same side on which it is
given.

page_text: The details of the aforesaid improvements are represented on the
annexed Sheet of Drawings, in which similar letters refer to like or
corresponding parts.
Fig. 1 is a plan, and Fig. 2 side elevation of one of my lever escape-
ment constructions.
Fig. 3 is a plan, and Fig. 4 side elevation of another of my lever
escapement constructions.
+
Fig. 5 is a plan of my simplest form of escapement.
In Figs. 1 and 2 (as well as in the other Figures) is clearly shewn
my mode of constructing. The roller B which has a jewel or other
pallet F placed in the middle of the small crescent-shaped hollow
cut in its edge; the pallet F engages with the two upright pins or
pallets C, C, which are placed on the lever A which turns on the
fulcrum K.
The escapement wheel M, which I prefer to make of steel and with 1
gold teeth so as to lessen the weight, and also the friction on the
pallet, is made with ten teeth only instead of fifteen, as heretofore
usual, and I make the pallets N, N, to embrace 1½ spaces only.
instead of 2, whereby the necessity for oil on the wheel pallets
is quite or nearly obviated because of the decreased height the pallet 2
has to be moved in order to receive the usual degrees of motion.
The wheel M is placed between the pallets N, N, and the balance
staff R whereby the pressure on the pallet pivots is lessened, as the
force is transmitted on the same side on which it is given. The yielding.
banking piece P is mounted freely on the axis L, but kept in position 2
by the controlling spring D. P is the yielding banking piece, and.
G, G, the banking pins on the same; E is the unlocking pin which
is placed as near as possible to the centre of the roller B (or it might
be placed on a separate roller, or on the balance staff itself). I thereby
obtain an almost complete separation of the unlocking. and impulse 9
action, and I also obtain a larger vibration of the balance because
the unlocking takes place under the circumstances of a more favourable
leverage, and a consequent diminished friction as compared with those
lever and roller actions in which one pallet or ruby pin only is used.
The resilient action is as follows:-The unlocking pin E, after having 3
traversed a full turn from the position of rest without having. finished_

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Sixth. The construction of the roller B with crescent notch, and
with the impulse pallet F in the said notch when constructed as here
described and shewn, that is, so as at the same time to form a safety:
action.
In witness whereof, I, the said William George Schoof, have here- t
unto set my hand and seal, this Tenth day of April, in the
year of our Lord One thousand eight hundred and seventy-.
four.