CERTAIN IMPROVEMENTS IN THE CON- STRUCTION OF TIMEKEEPERS
Year: 1851

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
MCDOWALL, of Hyde Street, Bloomsbury, in the County of Middlesex, Chro-
nometer Maker, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Tenth day of April, in the fourteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Charles McDowall, Her especial license, full power, sole privilege and autho-
rity, that I, the said Charles McDowall, my exors, admors, and assigns, and
such others as I, the said Charles McDowall, my exors, adññors, or assigns,
should at any time agree with, and no others, from time to time and at all
times during the term of years therein mentioned, should and lawfully might
make, use, exercise and vend, within England, Wales, and the Town of
Berwick-upon-Tweed, my Invention of "CERTAIN IMPROVEMENTS IN THE CON-
STRUCTION OF TIMEKEEPERS;" in which said Letters Patent is contained a pro-
viso, obliging me, the said Charles McDowall, by an instrument in writing
under my hand and seal, particularly to describe and ascertain the nature of
my said Invention, and in what manner the same is to be performed, and
to cause the same to be inrolled in Her Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
in part recited Letters Patent, as in and by the same, reference being there-
unto had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles McDowall, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, is particularly described
and ascertained in and by the following description thereof, reference being
had to the Drawings hereunto annexed, and to the letters and figures marked
thereon (that is to say):
The object of the present Invention is to simplify the construction of that
part of timekeepers known as the "escapement," and thereby reduce the
cost of the manufacture, and at the same time to ensure a more satisfactory
result than can be obtained by the use of the most perfect escapement hitherto
constructed. My Invention is capable of being applied under a variety of
forms or modifications of construction, but in all the same principle of action
is retained, whether the Invention be applied to the ordinary house clock,
astronomical regulator, or a pocket chronometer. In the several forms in
which it is set forth in the Drawing forming part of this my Specification the
Invention is shewn in the substitution of an excentric pin or a one-toothed
wheel (driven by the "train") in lieu of the ordinary "scape wheel," and the
use of a more simple construction of pallet than that heretofore employed.
I will now proceed to èxplain the action of the mechanism by reference to
the Drawing. Figures 1, 2, 3, and 4, shew one arrangement in different
positions. In this arrangement A is the end of an arbor or axis, on which
there is a pinion driven by the clock train in the usual way, the numbers of
the teeth in the wheels and pinions being so calculated and arranged that, as
the arbor A turns once round for every two beats of the pendulum, it will
allow the wheels that carry the hands of the clock to move at the required
speed over the dial. On the arbor A is fixed a small disc, from one side of
which projects a short pin P, set parallel to the arbor, and revolving in a circle
around it as the arbor is made to rotate by the action of the clock train.
This disc, with the pin P, is the substitute for the usual scape wheel; C is an
arm vibrating on an arbor at E, parallel to the other arbors of the clock
wheels, like the usual pallet-arbor; and B, D, are the pallets in which the
pin P acts. The pendulum is attached to the arbor E, (or it may be attached
to the arm C itself), in the same way as a pendulum is usually attached to the
pallets. The proportion between the length of the arm C and the distance of
the pin P from the arbor A ought to be such that the angle of escape of the
pendulum shall not exceed two degrees. By reference to Fig. 1 it will be
seen that the pin has just dropped from the pallet B on to D. If the pendulum
with the arm C is now moving to the left it will vibrate a little farther in that
direction, and the arm C will take the dotted position of Fig. 1, the pin

page_text: meanwhile resting on the upper surface of D, which is part of a circle, of
which E is the centre. When the vibrating arm returns again to this position,
and proceeds to the right, the pin will pass the corner of D and come into the
position shewn at Fig. 2, and thereby give an impulse to the arm in the direc-
tion of the arrow. On the arm vibrating a little farther to the right (as
shewn at Fig. 3), the pin will fall off the pallet D on to B, and rest on the
lower surface of B (which is also part of a circle, having its centre at E), until
the arm in making its return vibration from the dotted position of Fig. 3
comes again into the drawn position of that Figure. As it continues its
advance to the left the pin will, by reason of the continued rotation of the
arbor A, pass the corner of B (as shewn at Fig. 4), and give an impulse to the
arm in the direction of the arrow, driving it again into the dotted position of
Fig. 1, when the several movements above set forth will be repeated. The
action of the parts it will be seen is that of a dead-beat escapement.
In the
Drawing the impulse pin is shewn as cylindrical, but it may be a curved tooth
or cam if required.
Fig. 5 shews an arrangement in which the pendulum is made to carry
the pallets, the vibrating arm C being in this case dispensed with, and the
pallets being formed by a right-angled slot cut in a cross bar of steel. The
action of the parts is precisely similar to that above described.
Figures 6 and 7 shew a modification of the Invention as applied to the
balance wheel of a watch or portable timekeeper. A is the arbor, which com-
municates motion from the train through the disc and excentric pin P to the
detent lever C, which lever acts upon the roller of the balance wheel in the
ordinary manner. This lever is slotted at one end (as shewn at Fig. 6) to
form the pallets B, D, on which the pin P acts to give the impulse in opposite
directions, as above explained, and effect the temporary release of the pin and
allow of the required progressive motion of the train.
In all these arrange-
ments I prefer to construct the pin of a ruby, or other hard precious stone, to
remove all unnecessary friction; but, for the sake of economy, stcel or any
other suitable metal may be used.
Having now set forth the nature of my Invention, as secured to me under
the herein-before in part recited Letters Patent, I wish it to be understood
that I do not confine myself to the arrangements above described, and shewn
in the Drawing, as it will be evident that the objects I desire to attain may be
accomplished in various ways, without departing from the nature of the Inven-
tion; but whatever the modifications of form this new escapement may assume,
it may (besides effecting a considerable economy in the manufacture of dead-
beat escapements), be considered to possess this peculiarity (viz'), that it will

page_text: impart an impulse to the pendulum or balance while in the middle of its vibra-
tion chiefly by a direct instead of an oblique action.
In witness whereof, I, the said Charles McDowall, have hereunto set
my hand and seal, this Second day of September, in the year of our
Lord One thousand eight hundred and fifty-one.