Year: 1888

page_text: I, ALBERT LYMAN PARCELLE, a citizen of the United States, of Boston, Suffolk
County, Massachusetts, now residing in New York, County and State of New York,
U.S.A., Electrical Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement:
-
The object of my invention is to in prove the regularity and action of pendulum
clocks.
The invention consists, generally stated, in the employment of a resilient pendulum
clamped at one end. Heretoforo two kinds of pendulums have been used, viz.: a
straight pivoted pendulum and a straight pendulum suspended by a short thin
suspension spring. My pendulum is distinguished from these by the fact that it is
formed of a resilient body held firmly at its upper end so that it vibrates under
conditions other than those of the ordinary pendulum, as appears from the following
description. The invention also consists in a pendulum formed of a continuous strip
of resilient material so that in vibrating it not only bends at or near its point of
suspension but also in its length or body and this fact clearly distinguishes it from the
ordinary pendulums above mentioned. The purpose of my invention is to produce a
pendulum which will describe a perfect or approximately perfect cycloidal are, and
will therefore vibrate long and short arcs in the same time: And will by reason of
its resiliency tend to continue in vibration much longer than the pendulums now in
use. An incidental feature of my invention, of considerable importance, is its automatic
compensation described below.
In the accompanying drawings-
Fig. 1. is a front elevation illustrating, without elaboration or detail, a weight
driven clock-train equipped with my improved resilient pendulum.
Fig. 2. is a side elevation of the same; and
Fig. 3. is a diagram view illustrating the path described by the end of a pendulum
resilient throughout its length.
A clock pendulum which describes a segment of a circle in swinging is influenced
entirely by gravity, its velocity being determined by the distance it falls in reaching

page_text: its lowest point, or perpendicular position. It is well-known that the long and short
ares of such a pendulum are not made in the same time, and hence it is not isochronous,
except under certain conditions, which are very difficult to maintain.
Ordinarily, the pendulum of a clock receives the impulses which maintain it in
vibration from a weight or spring acting through a train of wheels. The wheels and
pinions of the train, however carefully they may be made, are not perfect either in
material or workmanship. The oil used to lubricate them becomes stiff, particles of
dust accumulate on the wheels, and their bearings, and some of the parts are worn
more than others. The impulses imparted to the pendulum will, therefore, vary more
or less according to the condition of the train. If a weight is used as a driver, as the
weight runs down the weight of the cord is added to the weight; and if a spring be
used as a driver, the power applied is still more variable, because as the spring uncoils
the force of the impulses imparted by it to the pendulum decreases.
These facts are mentioned to illustrate the difficulty of imparting to the pendulum
impulses of uniform power. Consequently the are of vibration is not uniform, and
the pendulum is not isochronous. A pendulum which describes a cycloidal arc is,
however, isochronous, whatever may be the variation, within certain limits, of the longth
or amplitude of its vibration.
In the drawing A represents an ordinary clock-train drivon by a weight A¹. 6 is
an ordinary clock-scapement. The pendulum P is adjustably clamped at its upper
end in a split-post p. The lever c is connected with the spindle of the pallet, and is
carried down and embraces the pendulum, as usual.
My improved pendulum here illustrated may be formed of any suitable resilient
material. It may be made, for instance, of steel, whalebone, wood, glass, hone, etc.,
or any other resilient material, and preferably of such material as is not influenced or
subject to change on account of variations of temperature and moisture. It is capable
of bending from end to end, and it is preferably in the shape of a flat, thin bar of the
general character shown in the drawings. A pendulum of this character is isochronous
for all amplitudes of vibration required in a clock. To operate at the same rate or
number of beats as a gravity pendulum, it may be longer or shorter than such a
pendulum. It is not governed by the same laws that control an ordinary pendulum,
but is dependent upon two conditions, namely its length and thickness. Gravity does
not primarily control its action as its own inherent resilience serves to return it to the
centre of vibration or perpendicular position.
My improved pendulum is preferably equipped with a bob which may be a hollow
cylindrical cup adapted for the reception of sand or shot, or any other suitable
weighting material. The bob may be adjusted for regulation in the ordinary way by
a thumb-nut on the screw-rod extension of the pendulum. A bob may or may not be
used. Its effect would be to add steadiness, but it may be dispensed with, or a very
light one used, according to the material used for the pendulum. Where a bob is
employed it will very slightly-according to its weight modify the arc.
The pendulum may be compensated by any of the ordinary methods, but has the
advantage of being partially self compensating. A change of temperature which
would clongate it would also tend to increase its thickness. This automatic compensation
is sufficient for ordinary clocks.
The diagram view, Fig. 3, illustrates the character of the arc described by such a
pendulum as that shown. represents a base or tangential line, y the arc described
by an ordinary pendulum, and the arc described by my improved pendulum.
My invention is distinguished from ordinary clock pendulums having suspension
springs formed separately or by drawing down the end of a wire pendulum. Such
suspension springs serve merely as hinges upon which the pendulum—which is a gravity
pendulum-vibrates. In my improved device the pendulum proper bends in its length
in vibrating and when I use the term, bends or bending in its length, I mean the
rod, strip or bar forming the pendulum proper bends in vibrating to such extent
as to give it the character of an elastic vibrator, as herein set forth, as distinguished
from the bending of a mere suspension spring. For, by forming the pendulum of
resilient material and causing it to bend in vibrating, it is governed, at least in part

page_text: by the laws governing elastic vibrators, and is to that extent different from the ordinary
gravity spring-suspended pendulums. Preferably the spring pendulum is made to
bend throughout its entire length as more perfect results are believed to be attained
thereby.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what
1 claim is
1. The combination, substantially as set forth, of a driven train, a pendulum formed
of a bar or strip of resilient material rigidly held at its upper end and bending in its
length as it vibrates, and a scapement interposed between the pendulum and the
clock-train.
.
2. The combination, substantially as set forth, of a driven train, a pendulum formed
of a bar or strip of resilient material capable of bending throughout its entire length
as it vibrates, and a scapement interposed between the pendulum and train.
Dated this 94th day of Anril 1888
ALBERT LYMAN PARCELLE.