Im- PROVEMENTS IN LEVER ESCAPEMENT MECHANISM
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by William George Schoof at the
Office of the Commissioners of Patents, with his Petition, on the
6th November 1873.
I, WILLIAM GEORGE SCHOOF, of Clerkenwell, in the County of
Middlesex, do hereby declare the nature of the said Invention for “Im-
PROVEMENTS IN LEVER ESCAPEMENT MECHANISM," to be as follows :—
The objects of my Invention more particularly as regards watches are
to all but separate the "unlocking" action from the "impulse" action,
to do away with the "banking error," to prevent the pivots of the balance
from injury by the banking which now occurs in lever watches
through excessive vibration occasioned by violent movements of the
wearer of such watches, and which is especially necessary in high class
timekeepers, where a heavy balance and thin pivots and large arc of
vibration are a necessity; also to give additional security to the safety
action thereby making a double roller unnecessary; also to give the
balance a stronger impulse.
As my Invention to a certain extent refers to the same objects or
purposes I will here refer to the so-called two pin escapement invented
by Mr. Savage. This Invention was intended to separate the unlocking

page_text: action from the impulse action, and at the same time perform both as
nearly as possible in the line of centres of "the roller" and "the lever
of the escapement, also to perform the unlocking action nearer to the
roller centre than in the ordinary escapement. He attained these
objects to a limited extent only because it was found that unless the
notch in the roller was made much wider than otherwise necessary, the
impulse pin of the "lever" would under certain contingencies abut
agaist the back part of the notch or the part opposite to the impulse
side, the unlocking pins or jewel had therefore to be put much further
from the centre than originally intended. Now I attain the aforesaid
advantages by putting an impulse pin or jewel in the edge of the roller
instead of a notch as just mentioned, and I allow this impulse pin to
perform a fractional part of the unlocking action, whereby the aforesaid
abutting is prevented.
According to one mode where I however do not separate the impulse
action from the unlocking action, I place a pin or a ruby in the edge or
circumference of the roller in the centre of the crescent-shaped hollow
in the edge of the roller. This pin receives the impulse of the lever on
cach side alternately by two rubies or pins put into the lever vertically
to the surface of it, or two screws or projections filed out of the solid
lever, or a solid piece fastened on to the lever may answer the purpose,
and forming thereby the "notch" of the ordinary lever. In this form
of escapement the unlocking is done by the same pin or pallet that
receives the impulse. I thus do away with both the prongs and horns of
the ordinary lever which now serve as a safeguard against the return
movement of the lever, because the aforesaid two pins embrace the
impulse pin long enough as to bring the opposite crescent-shaped edge
of the roller in position to prevent the return of the lever by engaging
with the other of the two pins. I am thereby also enabled to get a
very sound and simple "resilient " action, which shall be described
presently.
According to another arrangement I separate the unlocking from the
impulse action by placing a single pin of ruby or other suitable material
much nearer to the centre of the roller than ordinarily done, and
allowing it to unlock by means of a fork the prongs of which are so far
apart as to commence the unlocking very near to the line of centres,
I cause a piece of ruby inserted in a slit in the edge of the roller or a
pin, or screw, or jewel in the edge of the roller to perform the last
and

page_text: fractional part of the unlocking movement as aforesaid. The 'same
action may be obtained by a pin, or screw, or a slip of ruby or other
suitable material inserted in the balance arbre direct or in another
separate roller fastened on to the arbre.
I give the lever a resilient. or elastic banking action in the following
manner :-I place the two banking pins which ordinarily are in the
plate or frame into a separate bar plate or piece of metal, which can
freely move on a fulcrum or centre placed as far from the banking pins as
the construction of the watch or other timepiece will conveniently allow,
and kept in its normal position by a spring. The action is as follows:-
The unlocking pin after having traversed a full turn from the position
of rest without having finished its motion will strike against the back of
one of the prongs of the lever, which resting against one of the banking
pins or other suitable projection on the aforesaid yielding banking piece
will throw it back so far as to allow the unlocking pin to pass the prong,
thereby preventing the too quick repetition of vibration, which is called
the banking error.
Another arrangement for this purpose is as follows:-To the lever or
to its arbre or to the pallet attached to the lever I attach a spring
having two legs, the outer ends of which are made to enter the prongs
of the lever so that the action takes place against them instead of against
the prongs themselves. I prefer to make these legs in one piece or
length bent flat, and at the bend fastened into a little stud passing
through the lever, and I also prefer to make this spring or springs or
legs as long as convenient. The action is similar to the one just
described, only that here the spring or springs are pressed against direct,
whereas in the former case the banking pins yield; the banking pins or
planes or surfaces in this case however are unyielding or rigid.