AN IM- PROVED CONSTRUCTION OF ÅÁSTRONOMICAL CALENDAR
Year: 1853

page_text: LETTERS PATENT to Louis Achille Brocot, of Paris, in the Empire
of France, Clock Manufacturer, for the Invention of "AN IM-
PROVED CONSTRUCTION OF ÅÁSTRONOMICAL CALENDAR "
PROVISIONAL SPECIFICATION left by the said Louis Achille
Brocot at the Office of the Commissioners of Patents, with his
Petition, on the 12th September 1858.
I, LOUIS ACHILLE BROCOT, do hereby declare the nature of the said
Invention for "AN IMPROVED CONSTRUCTION OF ASTRONOMICAL CALENDAR "
to be as follows:―
This Invention consists in a novel arrangement of mechanical parts
combined together in one instrument for indicating with correctness
the days of the week and the month, the phases of the moon, the
equation of time, and the hour of the rising and setting sun, in every
day of the year.
All these phenomena are indicated by pointers or hands, which revolve
in front of a dial resembling a clock face; the figures, letters, and
devices to indicate the several phenomena being arranged in the most

page_text: The
convenient manner to indicate clearly and without confusion.
days of the month and the days of the weck are marked on small
dials or circles, which are placed inside the principal or outer circle,
which indicate the name of the month and the equation of time in
such a manner that at any particular day of the year it can be seen
whether the clock or mean time is faster or slower than solar time.
The index of the dial to shew the day of the month is mounted on
the axle or pivot of a ratchet wheel provided with thirty-one teeth.
This wheel, as well as a smaller ratchet wheel with seven teeth to
operate the index for the days of the week, is actuated every twenty-
four hours by levers and clicks, which are governed by stop wheels for
the purpose of effecting the changes at the end of the month. The
moon's phases are indicated through an opening at the upper part of
the dial, past which a figure of the moon is made to pass by means of
suitable gearing, which causes the disc on which the figure of the
moon is marked to rotate once in every twenty-eight days.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Louis Achille Brocot in the Great Seal Patent
Office on the 11th March 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
LOUIS ACHILLE BROCOT, of Paris, in the Empire of France, Clock
Manufacturer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of September, in the
year of our Lord One thousand eight hundred and fifty-three, in the
seventeenth year of Her reign, did, for Herself, Her heirs and succes-
sors, give and grant unto me, the said Louis Achille Brocot, Her special
license that I, the said Louis Achille Brocot, my executors, administra-
tors, and assigns, or such others as I, the said Louis Achille Brocot,
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain

page_text: and Ireland, the Channel Islands, and Isle of Man, an Invention for
"AN IMPROVED CONSTRUCTION OF ASTRONOMICAL CALENDAR," upon the con-
dition (amongst others) that I, the said Louis Achille Brocot, by an
instrument in writing under my hand and seal, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Soal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Louis Achille Brocot, do hereby.
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the Drawing here-
unto annexed, and to the letters and figures marked thereon (that is
to say):
This Invention consists in a novel arrangement of mechanical parts
combined together in one instrument for indicating with correctness
the days of the week and the month, the phases of the moon, the
equation of time, and the hour of the rising and setting sun, in every
day of the year.
All these phenomena are indicated by pointers or hands which
revolve in front of a dial resembling a clock face; the figures, letters,
and devices to indicate the several phenomena being arranged in the
most convenient manner to indicate clearly and without confusion. The
days of the month and the days of the week are marked on small dials
or circles placed inside the principal or outer circle, which indicates
the name of the month and the equation of time in such a manner
that at any particular day of the year it can be seen whether the clock
or mean time is faster or slower than solar time. The index of the
month to shew the day of the month is mounted on the axle or pivot
of a ratchet wheel provided with thirty-one teeth. This wheel, as
well as a smaller ratchet wheel with seven teeth to operate the index
for the days of the week, is actuated every twenty-four hours hours by
levers and clicks, which are governed by stop wheels, for the purpose of
effecting the changes at the end of the month. The moon's phases are
indicated through an opening at the upper part of the dial plate, behind

page_text: which a figure of the moon is male to pass by means of suitable
gearing, thereby causing the disc on which the figure of the moon is
marked to rotate once in cvery twenty-eight days.
Having explained the objects and general features of the Invention,
I will now proceed to describe more in detail the arrangement, con- 5
struction, and operation of the various parts of which the improved
astronomical calendar is composed.
The mechanism represented in Figures 1, and 2, of the accom-
panying Drawing, although somewhat different in arrangement, is so
analogous in character, that one description will suffice for both of
these Figures, similar letters of reference being marked upon corre-
sponding parts in both Figures.
The ratchet wheel A, of thirty-one teeth, serves to indicate the days
of the month; and a small wheel B, of seven teeth, indicates the days
of the week. The shaft of the wheel A, Fig. 2, carries a pinion
having thirteen teeth, which gears into two wheels; the one marked C,
has one hundred and fifty-six teeth, and performs a revolution in the
space of a year. On the wheel C,
mounted a cam wheel D, which
has four portions cut away at suitable distances corresponding with
those onths having thirty days; and a fifth portion or nick cut deeper,
which corresponds with the month of February, for all years except
leap years. The remaining portions of the circumference of this cam
wheel, or those which have the largest diameter, correspond to those
months consisting of thirty-one days.
A wheel of one hundred and forty-four teeth, which has the same
diameter as the wheel C, (and being behind this latter is not shewn in
the Drawing,) and which I shall call C, is mounted upon a hollow
shaft upon the same axis, and also takes into the pinion of thirteen
teeth. This wheel C¹, is also provided with a second cam disc D',
concentric with that D, nine twelfths of the circumference of which
are on a level with the February nick of D, (behind which it is situate,
and is therefore not seen in the Drawing. These two cam wheels D,
and D', are represented detached at Figures 1ª, and 1b.) The other
three twelfths of the circumference of the cam D', which are of larger
diameter, project beyond the other parts, and are equi-distant from each

page_text: other, and come every four years opposite the February nick of the
cam D, for the purpose of diminishing its depth, and producing the
month of twenty-nine days for leap year.
It will be understood that the wheels C, and C³, both taking into the
same pinion will not perform their revolution in the same time, as one
of them has twelve teeth more than the other; the result of which will
be that when the wheel C, of one hundred and fifty-six teeth has per-
formed a revolution, the wheel C, behind it, of one hundred and forty-
four teeth, will have made one complete revolution and one twelfth of
another, the result of which will be that when the wheel C, has per-
formed twelve revolutious (that is, when twelve years shall have
elapsed), the wheel C, will have made thirteen complete revolutions,
and consequently every four years one of the three projections of the
cam wheel D, will come opposite to and diminish the depth of the
February nick.
Three studs E, F, G, are set upon the face of the wheel A, in such
manner that on being acted upon and pushed to a certain distance by
the pawle O, (hereafter described,) the equal course of each of them
shall correspond for the stud E, furthest removed from the centre to an
angular movement of two teeth of the wheel A, for the stud F, to three
teeth, and for the stud G, to four teeth. The detent lever H, h, is pro-
vided on its smaller arm h, with a pin i, which rests upon the circum-
ference of the cam wheels D, and D₁; and according to the position of
this pin upon the highest portions of its periphery, or in the nicks, the
curved piece K, at the extremity of the long arm H, will either be
below one of the three studs, or will even cover the stud E, which is
situate the furthest from the centre. In the position represented in
the Figures the three studs are all uncovered, which allows the pawle O,
to act upon the stud G, and impart to the wheel a movement equal to
four teeth.
Upon the detent L, to which motion is communicated every twenty-
four hours by the striking wheelwork, pawles M and N, Fig. 2, are
mounted, the former of which moves the wheel A forward one tooth,
and the latter the wheel B, one tooth. The tail of another pawle or
O, rests upon the curved end K, of the detent lever; and during the

page_text: months when this curved portion covers the pin or stud E, which is
furthest from the centre, this pawle will slip over the curve without
meeting with any obstacle, and the months will consist of thirty-one
days. When the curved arm has uncovered the pin E, the pawle O
will act upon that pin after the thirtieth day, and move the wheel for-
ward two teeth, which will produce months of thirty days. When the
stud G, which is nearest the centre, is uncovered, the pawle O, being
always driven over the same space by the action of the detent L, will
act upon that pin after the twenty-eighth day, and drive the wheel
forward four teeth for the month of February of those years which
are not leap years. Lastly, when one of the projections of the cam
wheel D', arrives opposite the February nick of the cam wheel D, and
diminishes its depth, the curved arm K, arriving in the neighborhood
of the stud F, the pawle O will act upon that pin after the twenty-
ninth day, and move the wheel forward three teeth for the month of
February of the leap years.
It will be understood that if upon the axle of each of the wheels A,
and B, a needle be placed corresponding to the centre of a dial, we
shall have for the wheel A, the days of the month, and for the wheel B,
the days of the week. The common axle of the cam or guide wheels D,
and D', may also carry a needle for indicating the months; and as this
needle only makes one movement during the day, it may at the same
time indicate upon the same dial figures shewing the equation of time
(see Fig. 3.)
The indication of the phases of the moon may be obtained by placing
upon the same axle as the wheel B, a pinion of sixteen teeth, taking
into and driving a wheel of one hundred and thirty-five teeth con-
nected with a disc, upon the white face of which are painted two blue
circles diametrically opposite to each other. These blue circles pass alter-
nately under a circular opening in the dial, which is itself painted blue
on those parts which surround the opening. The result of this
arrangement is, that every day a greater or less portion of the white
part, and also of a blue circle, is visible through this opening, which pro-
duces successively the appearance of the waxing or waning of the moon.
A complete revolution of the wheel will therefore correspond to two

page_text: lunations if the number of teeth chosen for the pinion and the wheel
be correct. The time included between two lunations is 59-0612.
Now the lunar wheel having one hundred and thirty-five teeth, and the
pinion of sixteen teeth which drives it making a revolution in seven
days, we have the following proportions:-16: 7 :: 135: 59-0625.
There will therefore be for two lunations an error of 0013 of a day,
which would in a period of one one hundred and twenty-five years
amount to an error of a day.
The arrangement represented in Fig. 4, differs but very little from
the preceding, the detent H, h. (Figures 1, and 2,) being in this case
replaced by a rack lever R, r, which takes into and drives the wheel S,
on which is mounted a disc T, placed at a short distance behind, and
having a projection or cam piece on its periphery. This wheel S, is
mounted loosely upon the shaft of the wheel of thirty-one teeth, which
serves as its spindle. One of the arms of the rack lever is maintained
in constant contact with the circumference of the cam wheel D, by
means of a spring, so that the rack will take a different position
according to whether the arm r, is in a nick of greater or less depth,
or upon one of the projections, which will cause the projecting or cam
part of the disc T, to assume different positions by means of the wheel
S, on which it is mounted, and which is governed in its movements by
the rack R, that takes into it. A single stud G, which is capable of
passing under the projection of the disc T, is fixed upon the face of the
wheel A, at such a distance from the centre that it will be uncovered
when the movement of the wheel A, shall have carried it beyond the
projection or largest diameter of the disc T. The pawle O, mounted
upon the detent L, will act upon the stud G, when this latter is un-
covered, and move the wheel round a distance of two, three, or four
teeth, according to whether the stud has been uncovered on the
thirtieth, the twenty-ninth, or the twenty-eighth day of the month,
which will be determined by the falling of the rack lever into one of
the nicks of the cam or guide wheel D.
The parts are arranged in such a manner that when the arm 1, of
the rack lever R, rests upon one of the projections or largest diameter
of the wheel D, (that is to say, for the months of thirty-one days,) the

page_text: end of the pawle O, will always rest upon the largest diameter or pro-
jection of the disc T, and can never reach the stud G, so that the
wheel A, will only be acted upon by the pawle M, and will only be
moved one tooth, which will produce thirty-one days to the month.
When, on the contrary, the arm r of the rack lever rests in one of the E
depressions of the wheel D, appertaining to the months of thirty days,
the stud G will be uncovered, and may be acted upon by the pawle O,
after the thirtieth day, in order to move the wheel forward two teeth.
When the arm r, of the rack lever R, rests in the February nick, and
the projection of the second cam wheel D', situated behind the wheel
D, has been thereby decreased in depth, (when, in fact, it is leap year,)
the stud G, will be further uncovered by the disc T, and that stud will
be acted upon by the pawle O, after the twenty-ninth day, and the
wheel A, moved forward three teeth, which will produce a month of
twenty-nine days. For ordinary years, the February nick having its
whole depth, the stud G will be further uncovered, and the pawle O
may act upon it after the twenty-eighth day, and move the wheel A
forward four teeth, which will produce a month of twenty-eight days.
Fig. 5, represents another mechanical arrangement; and although it
is intended to effect the same object as those above described, it differs
so materially from them as to require a separate description. Threo
wheels, the one A, having thirty-one teeth, B, seven teeth, and C,
twelve teeth, are acted upon in the following manner:-The two first
every day; the wheel A, by the pawle or lever M, mounted upon the
detent L; and the wheel B, by the pawle N; each of them being only
thereby moved forward one tooth, although the course of the detent is
much more extended than would be necessary merely to effect that
object, because as soon as the wheel A, has moved to the extent of one
tooth, the pawle or lever M, will come in contact with a pin H, and
will thereby be raised from the tooth which it has just moved forward.
The two wheels A, and B, also indicate the days of the month and of
the week, as in the other Figures. With respect to the wheel C, as
its object is to shew the months, and it only moves on the thirty-first,
the thirtieth, the twenty-ninth, or the twenty-eighth day, the pawle O,
which serves to communicate that movement to it, only comes in

page_text: contact with one of its twelve teeth at one of those periods, and passes
over that tooth during the whole month, at the end of which the
mechanism which will be presently described imparts a slight move-
ment to the wheel C, and brings the tooth into contact with the pawle
O, which imparts to it one twelfth of a revolution. On the same shaft
as the wheel C, and behind the wheel C, is mounted a second wheel C³,
taking into another wheel D¹, mounted on the same shaft as the cam
or guide wheel D. In the circumference of this guide wheel D, are
cut twelve nicks of different sizes, according to whether they belong to
months of thirty-one or thirty days. The size of the February nick is ren-
dered variable by means of a small wheel D", which will be hereafter
described. Upon the face of the wheel A, is set a stud G, at such a
distance from the centre that it will take into a nick of the wheel D,
towards the end of the month, and will on the last day of the month
come in contact with that side of the nick opposite to that at which it
entered. At the moment when, by the action of the detent L, the pawle
M acts upon and moves the wheel A, the stud G will also move forward
the wheel D. This latter cannot, however, move without communi-
cating an equal movement to the wheel C, as the two shafts of these
wheels C, and D, each carry a wheel of equal numbers of teeth, and
gear into each other. This movement of the wheel C, will consequently
again raise that one of its teeth over which the pawle O, passed during
the preceding month, and which now coming into contact with that
tooth will communicate to the wheel C, a twelfth of a revolution,
which acting upon the wheel D, will communicate to this latter the
same amount of movement. If the nick in which the stud G, is then
situate belongs to a month which contains less than thirty-one days, the
side of the nick at which the pin entered again acts upon the stud, and
moves it so as to drive the wheel A, forward one, two, or three more
teeth, according to whether it be leap year or not.
It will be seen from the foregoing description that the sides of the
nicks at which the stud G, enters are set at equal distances round the
wheel, and that the difference between them results from the greater
or less distance of the exit side; in other words, the movement of the
wheel A, two, three, or four teeth forward requires that the stud G,

page_text: shall come in contact at the exit side of a nick on the thirtieth, the
twenty-ninth, or the twenty-eighth day of the month; and that for
months of thirty-one days the contact shall take place on the thirtieth
and only serve at the time when the pawle M, moves the wheel A, one
tooth to determine the slight movement of the wheel D, and to bring
pne tooth of the wheel C, into contact with the pawle O.
: I will now describe the manner in which the indication of leap year
is obtained for the month of February:-Upon the edge of the wheel D,
is placed a small disc D", having a projection for producing the month
of February for leap year; this projection every four years diminishes
the breadth of the February nick of ordinary years. This disc D",
which is moveable on its axis, is kept in its place during the space of a
Fear by a spring resting upon two of the four pins set at right angles
upon its face.
At some period of the year, and at the moment when
the month changes, one of the studs on the disc D", comes in contact
with a fixed piece E, which forces this said disc to make a quarter of a
revolution, and at the end of four years thereby brings the projection
in front of the February nick, and decreases its breadth, in order only
to move forward two teeth to produce only twenty-nine days to the
month, as is requisite for the month of February of leap year.
The mechanism might be simplified, although with less certainty
in its results, by dispensing with the two wheels mounted on the shaft
of the wheels C, and D; and by making small nicks in the plain parts
of the wheel D, in which nick the points of the teeth of the wheel C,
take, which in this manner would act upon and be acted upon by the
wheel D. I, however, prefer the arrangements above described, as they
produce results of absolute certainty.
Fig. 6, represents the parts which are concealed by the dial. The
wheel R, of fifty-nine teeth is moved one tooth every day by the pawle
P, and serves to indicate the phases of the moon by the same means as
those above described. The disc S, is attached to the shaft of the month
wheel, by which it is carried round, and is divided into twelve parts,
upon each of which is marked the number of days contained in each
month, with the exception of that belonging to February. To indicate
the number of days in this month another disc S', divided into four parts,

page_text: is placed behind a small circular opening in the disc S; and on three of the
parts of the small disc S¹, are marked the numbers 28, representing the
number of days contained in the month of February of ordinary years;
upon the fourth part is marked the number 29, corresponding to the
number of days in the month of February in leap year. This disc S¹,
is mounted at about the middle of the radius of the disc S, by means
of an adjusting screw. It is provided on its flat face with four pins,
whereby it is kept in its place by means of a spring fixed upon the
disc. S. A stud fixed at U, will every year be brought in contact with
one of the four pins of the disc S, and impart to this latter one fourth
of a revolution, in order to place behind the opening in the disc S, the
number of days contained in the month of February, and marked on
the small disc St. Upon another disc T, which is divided into ten
year, which
parts, are marked the ten last numbers of months in the
appear successively through a small circular opening in the dial. This
disc is carried round every year by means of a stud set upon the
disc S.
The manner of indicating is represented in Fig. 7, in which the
equation of time is replaced by two sets of numbers, the red numbers
indicating the hours of the rising of the sun, and the black numbers the
hours of its setting.
In the above-described arrangements the needles move slowly,
because it is the striking movement that produces the backward and
forward movement of the detent L, which may in certain cases be situate
at some distance from the striking wheelwork, and must be in gear
during several hours, in order to produce accurate results.
Fig. 8, represents an arrangement whereby this is obviated, (that is
to say,) the movement of the needles or index hands takes place
suddenly and at midnight. In this arrangement a barrel A, serves to
put in motion the day detent L; for this purpose this barrel is provided
on its face with a number of studs or pins equal in number to the
number of days the barrel requires to make one revolution. The
barrel A, takes into a pinion æ, so arranged as to perform a revo-
lution in forty-eight hours. This pinion is provided with two arms
5 or wings set exactly opposite to each other, and which give it the ap-
pearance of a flyer. It will be understood that if any suitable stop be

page_text: applied to the wing of this flyer, and if this stop be disengaged at the
expiration of twenty-four hours at midnight, the flyer will perform half
a revolution, and during this time one of the pins of the barrel, by
taking on to the day detent L, will immediately communicate motion to
it. The wings of the flyer are disengaged every twenty-four hours by
means of a double cam cylinder y, shewn detached in perspective at
Fig. 8. This cam cylinder y, has two portions of its periphery cut
away exactly opposite to each other, and severally opposite to the two
wings of the flyer, and is mounted upon the shaft of a pinion that gears
into the striking barrel, and is of such diameter and number of teeth
as to perform a revolution in forty-eight hours. One of the wings of
the flyer bearing upon the cam y, will, when this latter has made half
a revolution, escape into the recess which will be presented to it, and
quickly perform half a revolution, and will then again bear upon the
larger diameter of the cam.
This arrangement presents the advantage of great facility in indi-
cating the days of the month. If, therefore, the barrel A, (Fig. 8,) be
so arranged as to perform its revolution in the space of thirty-one days,
and if the numbers 1, 2, 3, &c. up to 31, be engraved or marked upon
the flat face of the barrel so as to be visible through an opening in the
dial plate, these numbers will successively indicate the days of the
month thereon.
Fig. 9, shews another arrangement for effecting the same object. In
this arrangement the two wheels A, and B, are both mounted upon the
same shaft, although independent of each other; their number of teeth
are in the proportion of thirty-one to twenty-eight, and both take into
the pinion x, so that at each jump of the flyer the wheel A will be
carried round one thirty-first, and the wheel B one twenty-eighth of a
revolution, the one serving to indicate the days of the week, and the
other the days of the month, both these indications being visible through
a circular opening in the dial plate.
Fig. 10, represents another arrangement, in which the wheels A, B,
both take into the pinion x, as in Fig. 9, but in this instance they each
carry round a cylinder A', B'. Upon these cylinders are marked the
days of the month and of the week, which are also visible through an
opening in the dial plate.

page_text: In these three arrangements a circle of 31 may be adapted so as to
work by friction of contact upon the shaft of the wheel A, so as to
admit of its adjustment at the end of each month, when the months
only consist of twenty-eight, twenty-nine, or thirty days.
In conclusion, I desire it to be understood, that I do not claim as my
Invention the production by mechanical means of the successive indi-
cations of the days of the week and of the month, the phases of the
moon and the equation of time, as these results have been heretofore
obtained by mechanical means. And I would observe, that although I
have shewn and described various parts which may have been hereto-
fore employed for similar purposes, I have merely done so in order to
illustrate more fully the parts I believe to be new. But that which I
claim as my Invention, and desire to secure under the above in part
recited Letters Patent, is,-
First, the general arrangement of parts as herein shewn and de-
scribed, and particularly the use and application of the rack R, which
admits of the employment of a single pin or stud for moving forward
the wheels two, three, or four teeth, as may be required.
Second, I claim the arrangement represented at Fig. 5, in which the
movements are regulated by means of a guide wheel.
Third, the arrangements represented at Fig. 6, for indicating the
month of February, and also the final numbers of months of the year.
Fourth, the arrangement represented at Fig. 7, for shewing the
rising and setting of the sun.
Fifthly and lastly, the mechanical arrangements represented at
Figures 8, 9, and 10, for the several purposes above described.
In witness whereof, I, the said Louis Achille Brocot, have here-
unto set my hand and seal, the First day of March, in the year
of our Lord One thousand eight hundred and fifty-four
Witness,
DELETTRES.
LOUIS ACHILLE BROCOT. (L.S.)