CERTAIN IMPROVEMENTS IN CLOCKS AND OTHER TIMEKEEPERS
Year: 1840

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
JOHN DENT, of the Strand, in the County of Middlesex, Chronometer Maker,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Tenth day of September, in the fourth year of Her reign, did.
for Herself, Her heirs and successors, give unto me, the said Edward John
Dent, Her especial licence, full power, sole privilege and authority, that I, the
said Edward John Dent, my exors, adñññors,. and assigns, or such others as I,.the
said Edward John Dent, my exors, adiñiors, 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 expressed, should and lawfully might make, use, excrcise,
and vend, within England, Wales, and the Town of Berwick-upon-Tweed,
my Invention of "CERTAIN IMPROVEMENTS IN CLOCKS AND OTHER TIMEKEEPERS;"
in which said Letters Patent is contained a proviso that I, the said Edward.
John Dent, shall cause a particular description of the nature of my said.
Invention, and in what manner the same is to be performed, to be inrolled
in Her said 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 thereunto had, will more fully and at.
large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said'
Edward John Dent, do hereby declare my Invention to consist, -
Firstly, in giving the impulse to the pendulum of a clock at the centre of.
percussion, or as near as practicable to that centre
Secondly, in producing a compensation for the expansion and contraction
of the length of the pendulum arising from changes of temperature, by causing

page_text: the arcs of oscillation to vary.in an inverse ratio to the variations of the length
of the pendlum.
Thirdly, in combining three or more main springs and barrels to act simul-
taneously, without the medium fuzee, upon the train of wheels of a chronomer
or other timekeeper, whereby the maintaining power is increased without
employing thicker or wider springs than ordinary, and thus the action can be
made to continue eight days or longer from once winding up, and by using
that part of the springs only which is in a state of high tension.
Fourthly, in connecting three or more main spring arbors with a common
arbor, whereby all the springs may be wound up at the same time by one
application of the key.
Fifthly, in withdrawing, as much as practicable, the atmospheric air from
the interior of an air-tight case containing a chronometer, and in filling the
space-with a dry non-corroding gas, such as hydrogen, whereby the oil with
which the works of the chronometer are lubricated will be prevented from
oxydation, and will therefore remain in a fluid state, and continue to keep the
friction of the works. at a minimum, the quantity of the non-corrosive,
gas being
so regulated that its elastic force shall never, by expansion in the hottest climates,
become equal to the pressure of the atmosphere on the outside of the case, the
winding-up arbor of--the chronometer passing through and revolving in a
stuffing box, so packed that all communication between the contained gas-and
the external air shall be prevented..
And sixthly, in the application of the well-known voltaic or electro-metal-
Murgic process to the depositing of a thin film of gold or other metal, incorro
-dible by the atmosphere, upon the steel balance spring and the compensation
balance, the surface of which having been cleaned with alkali or acid imme-
diately previous to the application, in order that the metallic adhesion may be
perfect and rust prevented, and consequently one cause of variation in the rate
of chronometers-is-thus avoided._
And I hereby further declare that the manner in which I carry my-improve-.
ments into effect is particularly shewn in the Drawings hereunto annexed, as
explained by the description thereof herein contained, reference being had to
the figures-and-letters marked on the Drawings, in correspondence with the
figures and letters inserted in the description.
DESCRIPTION OF THE DRAWINGS.
Figure 1 represents in full size the lower part of a pendulum, oscillating
between two friction rollers, supported on the upper ends of two vertical rods
in connection with the pallets, detents, and wheel of what is termed a gravity
escapement.

page_text: Figure 2, a plan of a ring surrounding the cylinder of Figure 1, to carry
two expansion pieces.
The same letters refer to the same parts in both Figures.."
a, a solid cylinder of iron, suspended from the pendulum rod. b, a portion
of the pendulum rod. c, a screw on the end of the pendulum rod, for adjust-
ing the cylinder as to its length from the point" of suspension. ; a graduated
scale and index, for determining small degrees of adjustment. e,' a. ring
surrounding the cylinder, for carrying two compensation pieces by means of
two. clamps. e, the two clamps for holding the compensation pieces. f, the
compensation pieces, each composed of two laminæ of brass and steel, the
inner side of each piece being of brass and the outer side of steel. f¹, gradu-
ated lines drawn around the cylinder, by which the height of the ring'e may be
determined. g, two friction rollers, to communicate the impulse from the
escapement to the compensation pieces, and by them to the pendulum. h, two
vertical rods, carrying the friction rollers g, the lower ends of the rods sliding
in two. arms projecting horizontally from two arbors, which also carry the
pallets and detents. k, the two arms, projecting from the arbors. 1, 1, the
two arbors. m, two arms affixed obliquely to the arbors 1,. and carrying
the pallets, detents, and adjustable gravity weights: n, the pallets, having
the detents at their extremities. p, two adjustable weights, called gravity.
weights, for determining by their fall the force of the impulse on the pendu-
lum. 7, two screws at the lower extremities of the oblique arms m, for
regulating, the depth to which the pallets shall fall between the teeth of the
escapement wheel. 'r, two cauking pieces, to determine the depth of the fall
of the pallet arms. s, the escapement wheel; the weights p being adjusted to
give a sufficient degree of impulse to the pendulum to cause it to describe an
arc just large enough to lift the opposite, detent. It is obvious that an increase
of temperature, lengthening the pendulum, will at the same time throw out
the compensation pieces f, and cause them to strike the rollers g with shorter
arcs of oscillation, and consequently the tendency to slower oscillations occa-
sioned by the elongation of the pendulum will be counteracted by the tendency
to quicker oscillations from the reduction of the arcs. An exact compensation
will be arrived at by making the compensation pieces longer or shorter, and
adjusting them higher or lower upon the pendulum.
Figure 3, example of a plan of the apparatus for winding up four barrels at
one application of the key.-a, the square of the winding-up arbor, on which
the key is applied. b, a plate or bridge, screwed down upon the upper plate
of the chronometer, for supporting the upper pivot of the winding-up arbor.
c, three screws, by which the plate b is secured to the upper plate. d, the
upper plate, in which is supported the under pivot of the winding-up arbor,

page_text: through which plate also the arbors of the four barrels pass. e, three screws
for securing the upper plate down upon the pillars of the pillar plate of the
chronometer. f, a ratchet wheel, click, and springs, shewn by dotted lines,
.for holding the winding-up arbor against the force of the main springs. g, a
wheel fixed on the winding-up arbor, taking into and driving four wheels fixed
'on the four barrel arbors. h, the four wheels fixed on the four barrel arbors,
and driven by the wheel g. It is obvious, from this construction, that the
turning of the winding-up arbor, by the application of the key upon its square,
will at the same time turn all the four barrel arbors, and therefore will wind
up all the four springs simultaneously.
Figure 4, example of a plan of the wheelwork, by which the forces of four
'main springs are made to act simultaneously upon the train of a chronometer.
-a, two wheels affixed on two of the main spring barrels, and driving a pinion b
at nearly opposite sides. b, a pinion, driven by the two barrel wheels a, having
on its arbor an intermediate wheel c. c, an intermediate wheel on the arbor of
the pinion b, and acting in the centre pinion g. d, two wheels, similar to those
at a, affixed to two other main spring barrels, and driving a pinion e at nearly
opposite sides.
e, a pinion, driven by the two barrel wheels d, having on its
arbor a wheel f. ƒ, a wheel on the arbor of the pinion e, and acting in the
centre pinion.g,. nearly opposite to the action of the wheel e. g, the centre
pinion, driven at nearly opposite sides by-the two intermediate wheels e and f.
This pinion, making one revolution in each hour, carries on its-arbor the
ordinary wheel which gives motion to the train in the usual manner. k, three
pillars. 1, the pillar plate. m, space left between the barrels for the train
and escapement to be placed.
.And I hereby further declare, that I lay no claim to the construction of the
pendulum represented in the Drawing.
And I lay no claim to the escapement, shewn in the Drawing.
And I lay no claim to the application of two main springs acting together
on one train of wheels.
And I lay no claim to the action of two barrel wheels driving-a-centre
pinion at nearly opposite sides.
And I lay no claim to the placing of a chronometer in an air-tight box,
uncombined with the introduction of a dry non-corrosive gas.
But I claim the right of giving the impulse to the pendulum of a-clock at
the centre of percussion, or as near as practicable to that centre, as herein-
before shewn and explained.
And I claim the right of producing a compensation for the expansion
and contraction of the lengths of the pendulum arising from changes of tempe-
rature, by causing the arcs of oscillation to vary in an inverse ratio to

page_text: the variations of the lengths of the pendulum, as herein-before shewn and
described.
And I claim the right of combining three or more main springs to act
simultaneously, without the medium of a fuzec, upon the train of wheels of
a chronometer or other timekeeper, as herein-before shewn and described.
And I claim the right of placing two intermediate wheels between the three
or more barrel wheels and the centre pinion, in order to make a chronometer
or other timekeeper to go eight or more days at one winding up, as herein-
before shewn and described.
And I claim the right of connecting three or more arbors of the main
springs with a common arbor, whereby all the barrel arbours may be wound
up at the same time by one application of the key, as herein-before shewn and
described.
And I claim the right of placing a chronometer or other timekeeper in an
atmosphere of dry non-corrosive gas, contained in an air-tight case, through
a stuffing box, in which case the winding-up arbor passes, and in which it
revolves, whereby all communication between the contained gas and the
external air is prevented, as herein-before particularly shewn and described.
And lastly, I claim the application of the well-known voltaic or electro-
metallurgic process to the depositing of a thin film of gold or other metal,
incorrodible by the atmosphere, upon the steel balance spring and compen-
sation balance, whereby rust is prevented, and consequently one cause of
variation in the rate of chronometers is avoided, as herein-before explained.
In witness whereof, J, the said Edward John Dent, have hereunto set
my hand and seal, this Ninth day of March, One thousand eight
hundred and forty-one