Improvements in Clocks.
Year: 1897

page_text: Improvements in Clocks.
I, WILLIAM GEORGE SCHOOF, of 99, St. John Street Road, Clerkenwell, London,
Chronometer Maker to the Admiralty, do hereby declare the nature of this inven
tion to be as follows:
A principal object of my invention is to reduce very considerably the power for
moving the clock mechanism and so also that even in the largest clocks the variable
resistances caused by the weight of the dial hands and the influence of the wind
are obviated. I also in the large clocks do away with all the usual train wheels.
I employ for a large clock an escapement wheel with say 3600 teeth or any other
large multiple of twelve and in connection therewith an escapement mechanism
presently to be described. The front wall of the clock has a segment shaped hole
of about an angle of 60° for three hour figures to show through the middle one
of which shows the time said hour figures being marked on a dial ring rotating
behind the front wall; the front wall has also a similar segment shaped hole for
three minute figures to show through said figures being marked on another dial
ring rotating around the hour ring behind the front wall and on the same level
as the first named dial ring. As there are no dial hands the influences of their
weight and of the wind are entirely obviated. The hour dial ring makes one
rotation in twelve hours and the minute ring one rotation in one hour. The
seconds will be observable by the periodical sudden movements or "jumps" of
the minute dial ring. The dial rings may be transparent and illuminated. The
segment holes are glazed in order to protect the interior of the clock. The escape-
ment wheel as well as the dial rings move from right to left. The escape wheel
with its hour dial ring, a pinion fixed thereto, an intermediate wheel and a
minute wheel with its dial ring thus constitute the dialling for a very large clock.
Where space is not available for so large an escape wheel as is necessary if it is
to turn only once in twelve hours, a fraction of twelve may be used by fixing the
hour dial on a separate arbor which by tooth wheel gearing is connected to the
escape wheel arbor. In order to render this construction practically possible I
employ escapement mechanism, whereby the so called "drop" for freeing the
pallets is converted into impulse which sustains the pendulum in its vibratory
motion. Furthermore whether the escapement is applied to the very largest
clock or to say a mantelpiece clock the chord of motion of the escape wheel is
made as long as to give the necessary degrees of motion to the pendulum. The
escapement wheel is by preference made with very short club teeth having radial
sides.
Another object of my invention is to do away with the great amount of friction
which generally obtains in gravity escapement mechanisms owing to the large
weight heretofore necessary for keeping the clocks going. For this purpose I use
an escape wheel with a much larger number of teeth than heretofore that is to
say from about 90 upwards instead of 30. Where I desire a clock to run for a

page_text: couple of years without being rewound, I use for a large turret clock for instance
an escape wheel with 3600 teeth and a six seconds pendulum. The clock line for
propelling the escape wheel is wound round the escape wheel arbor, thus unwind-
ing one turn for every twelve hours. The gravity arms move independently on
the same fulcrum pivot or on two separate fulcrum pivots or centres. Each arm
has a pallet; these serve the double purpose of arresting or locking the escape
wheel and of lifting the gravity arms off the pendulum rod, as soon as the latter
has unlocked the tooth of the escape wheel, when by its own momentum the
impulse is given which keeps the pendulum in vibration. Stops or banking pins
are provided which arrest the gravity arms in such a way that the unlocking
begins when the pendulum has arrived at the vertical centre line of the wheel.
The gravity arms are in the upper part provided with weight arms stiffly jointed
thereto but capable of being turned towards or from the line of centre for diminish-
ing or increasing the gravity, so that the impact takes place when the pendulumn
has arrived at its momentary stop or dwell before returning.
The lower ends of the gravity arms are jointed and carry the impulse pins
which embrace the pendulum rod, the joints are stiff but permit of the said ends
being turned; to put the pendulum in beat these ends are pressed against the
pendulum rod when it is at rest and the gravity arms bear on the banking pins.
As applied to an ordinary "regulator" or astronomical clock a wheel of 30
teeth is fixed on the front pivot of the escape pinion and gears with a pinion of 10
leaves which carries the seconds hand. The slack or back-lash of this gearing is
overcome by making the wheel double and connecting the wheels by a weak piece
of spring so as to hold them a few degrees apart before it engages the pinion.
But any other numbers of teeth may be chosen so long as it is in the ratio of three
They may be made of such size as will best suit the proportion of the
dial circle. In this way the seconds hand will turn from left to right as usual.
As compared with the double threelegged gravity escapement it will be seen
that there being only two degrees of train motion in the wheel with 90 teeth
per unit of time, it cannot gather up speed enough to trip and therefore requires
no fly on the escape wheel pinion to check it.
to one.
Assuming the force necessary to overcome the inertia of the two different wheels
to be equal viz. that the double threelegged wheel with its fly requires as much
force to set it in motion as the 90 toothed wheel without any fly, then the substir
tution of the larger wheel for the smaller will convert an 8 day clock into a 120
day clock without any extra weight or driving power.
But if it be preferred to remove a wheel and pinion from the train or in such a
way alter the train as to leave it an 8 day clock as before, then the weight now
required will only be one fifteenth of the former.
There is however another side to the question according to which the driving
power should be reduced much more than fifteen times, viz. the unlocking resist-
ance which the pendulum has to overcome is reduced to one fifteenth of that
which the double threelegged gravity escapement offers, and so requires less
impulse to keep up the same length of are of vibration.
Another feature in favour of 90 or 180 or more teeth is that this escapement
has no loss through "drop," in fact drop has been entirely utilized to lift the
gravity arms. By escaping the pallets over fewer teeth the lifting angle will be
increased to almost any desired extent. When however the wheel is not perfectly
true or not quite evenly divided some drop will have to be given; but the extra
drop required in the Graham escapement, to free the tooth of the wheel when the
pallets are moving towards the centre, is in my gravity escapement entirely
eliminated and turned into useful impulse.
If the two gravity arms were rigidly connected so as to move together as in the
Graham escapement there would be no gravity action, nor one that could keep
going for any longer time than is required for exhausting the impulse with which
the pendulum has been started. The reason for this is not far to seek. The 30
toothed wheel passes 6 degrees of train motion for each beat of the pendulum in

page_text: order to give one degree of impulse but a 90 tooth Graham wheel would only
pass 2 degrees and the pallets would for an extra free arc for safety's sake have
to run on the locking the same amount as they are not independent of each other
as in my escapement. The pendulum would receive no assistance to keep it
vibrating. The negative quantity that tends to stop the pendulum in a 90 or 180
tooth Graham escapement would now be equal to the positive quantity that causes
it to vibrate.
Thus the 90 or 180 toothed gravity mechanism (as compared with the 30 toothed
Graham) requires no drop and it has a fixed quantity to unlock whether the
vibrations describe large or small arcs. Moreover although I have only two
degrees of speed in the 90 tooth wheel or 1 degree in an 180 tooth wheel I can give
more speed by lessening the number of teeth over which the pallets escape. This
would be desirable when clocks with short pendulums are provided with gravity
escapement.
Now, as the pressure on the locking is inversely proportional to the radius of the
escape wheel it follows that there can be only one third of resistance to overcome
when the respective sizes of wheels are taken into account, so that the 90 toothed
gravity escapement should not require more than say two thirds of the weight
that the usual 30' toothed Graham escapement has all other conditions being the
same viz. the same pendulums and suspension springs, the same arc of vibration
and the same excellency of clock train construction and make.
To recapitulate in the 90 toothed escapement is sacrificed two degrees of train
motion; in the 30 toothed Graham six and in the double three legged gravity
thirty degrees of the train motion for each beat of the pendulum.
The wheel in this new escapement being necessarily large it should be planted
so as to work outside the pillar plate, close to the pendulum rod. The centre
wheel gearing into the escape pinion should be made as large as convenient and
have twenty times as many teeth as the escape pinion has leaves.
The objection which has been made to gravity escapements generally is that if
both arms are pulled out of gear together the wheel will run. To overcome this
a very simple device may if desired be applied whereby a spring is put in action
if both arms are pulled apart simultaneously.
Data T
J
1007
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
I, WILLIAM GEORGE ScHoor, of 99, St. John Street Road, Clerkenwell, London,
Chronometer Maker to the Admiralty, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement:
-
A principal object of my invention is to reduce very considerably the power for
moving the clock mechanism and so also that even in the largest clocks the variable
resistances caused by the weight of the dial hands and the wind are obviated.
I also in very large clocks do away with all the usual train wheels and pinions.
Another object of my invention is to do away with the great amount of friction
which generally obtains in gravity escapement mechanisms owing to the large
weight heretofore necessary for keeping clocks going. For this purpose I use an
escape wheel of much larger diameter and with a much larger number of teeth
than heretofore that is to say from 90 upwards instead of 30 or even much less.

page_text: "
My gravity escapement is so constructed that one of the gravity arms is always
in position to lock the escape wheel before the other gravity arm is unlocked;
and the so-called "drop on and off the pallets necessary for freedom in the
Graham escapement is in the case of my escapement converted into impulse.
Fig. 1 is a front view of a wall behind which a clock with a large dial is
arranged and Fig. 2 a horizontal section on line showing the dial and the
interior parts of the clock behind the dial.
The front wall A. has a bevelled segment shaped hole for say three hour figures
to show through the middle one of which (in this case XII) shows the time, said
hour figures being marked on a dial or ring B rotating behind the front wall A
and fixed on the escape wheel arbor K. The same segmental hole also shows three
minutes figures (in this case "55 ""60" and "5") the said figures being marked
on another dial ring C rotating around the hour dial ring B behind the front
wall A in the same vertical plane and revolving round the same centre as the
dial ring or disc B. As there are no dial hands the influences of their weight
and of the wind on them are entirely obviated. The hour dial B makes one rota-
tion in 12 hours and the minute dial C one rotation in one hour. The wheel I)
fixed on the arbor K of the escape wheel I gears with the pinion F which is keyed
or rivetted to a wheel E mounted on a stud or pivot and the latter wheel E gears
with the wheel G which travels round once in an hour. The arms H fixed on the
wheel G carry or engage with the outer or minute dial ring C. The outside of
the said ring is guided by the four or more rollers R in the same way as the date
ring in a grandfather's clock. The seconds or minute divisions will be observable
by the periodical sudden movements or jumps of the minute dial ring C. The
dial rings B and C may be transparent and illuminated, and the figures thereon
opaque. The segmental hole in the wall A is glazed in order to protect the
interior of the clock and a pointer or pointers X of any suitable construction is
or are provided. The escapement wheel I as well as the dial rings B and C move
from right to left.
Fig. 3 is a full sized front view of part of a large escapement wheel say 12 feet
in diameter showing the way that the pallets M of the gravity arms M would
engage therewith. This large escapement wheel is provided with 3600 teeth and
with its pendulum rod O and gravity escapement arms M would constitute the
whole of the working parts of the clock. On the escapement wheel would be
marked the figures of the hours and the minutes, the top figures indicating the
time and the rest of the dial might or might. not be screened off as described
with reference to Figs. 1 and 2. Dial hands special dial and train of wheels would
all be done away with. The clock line for propelling the escape wheel is wound
round a barrel attached to the arbor of the escape wheel I. With a six seconds
pendulum the motion of the gravity arms M might be only a fraction of a degree.
M* M* are cups for receiving shot or the like for adjusting or regulating the
weight of the gravity arms. Owing to the large reduction in the weight required
to drive a clock so constructed and to the corresponding reduction in the necessary
strength of the clock line such a clock might be arranged to run for say a year
with one winding: Where space is not available for so large an escape wheel as
is necessary if it is to turn only once in twelve hours, a fraction of twelve may he
used by fixing the hour dial on a separate arbor which by tooth wheel' gearing
is connected to the escape wheel arbor.
In order to render this construction practically possible I employ escapement
mechanism of the construction shown in Fig. 4 (as it would be used in a regu-
lator or other smaller clock).
The gravity arms M move independently as shown on two separate fulcrum
pivots or centres N or they may both be loosely mounted on a common centre.
Each arm M has a pallet M¹ and these latter serve the double purpose of alter-
nately arresting or locking the escape wheel I and of easing the said gravity
arms M off the pendulum rod O as soon as the latter has unlocked the tooth of the
escape wheel, and the weight of the gravity arm gives the return to the pendulum

page_text: as far as the line of centres on vertical plane. Stops or banking pins P are pro-
vided which alternately arrest the gravity arms M in such a way that the unlock-
ing begins when the pendulum O has arrived at the line of centres.
The gravity
arms M may in the upper part be provided with weighted arms Q stiffly jointed
thereto but capable of being turned towards or from the line of centres for
diminishing or increasing the gravity as may be required for adjustment.
The lower ends M3 of the gravity arms M are jointed and carry the impulse
pins M³ which embrace the pendulum rod 0; the joints are stiff but permit of
the said ends M2 being turned; to put the pendulum in beat, these ends M2 are
pressed against the pendulum rod when it is at rest and the gravity arms M bear
on the banking pins P or against the ends of a banking piece or lug. Further-
more, when the pendulum leaves the centre, it according to my invention comes
into contact with one of the impulse pins M³ and unlocks the escape wheel I
which then eases the said crutch pin M³ off the pendulum so that during the
return of the latter to the centre line the weight of the gravity arm gives
the necessary impulse for the rest of the vibration without "drop." Whether the
escapement is applied to the very largest turret clock or to say a mantel piece
clock the chord of motion of the escape wheel is made only so long as to give the
necessary impulse or length of travel to the pendulum. The escapement wheel
is by preference made with very short club teeth having radial sides as shown
and it is suitably mounted at the back of the pillar plate S.
As applied to an ordinary "regulator" or astronomical clock, a wheel of say
90 teeth is fixed on the front of the escape wheel arbour K and gears with a wheel
of 30 teeth, the arbor of which carries the second hand. The second hand is kept
steady by a weak spring touching its arbor.
The wheels may be made of such size as will best suit the proportion of the
dial circle. In this way the seconds hand will turn from left to right as usual.
As compared with the double three legged gravity escapement it will be seen
that there being only two degrees of train motion in the wheel with 90 teeth per
unit of time, it cannot gather up speed enough to trip and therefore requires no
fly on the escape wheel pinion to check it.
Assuming the force necessary to overcome the inertia of the two different wheels
to be equal viz. that the "double three legged wheel" with its fly requires no
more force to set it in motion than the 90 toothed wheel without any fly, then
the substitution of the larger wheel for the smaller will convert an eight day clock
into a 120 day clock without any extra weight or driving power.
But if it be preferred to remove a wheel and pinion from the train or in such
a way to alter the train as to leave it an 8 day clock as before then the weight
now required will only be one fifteenth of what it was originally.
There is however another side to the question according to which the driving
power may be reduced much more than fifteen times, namely, the unlocking
resistance which the pendulum has to overcome is reduced to one fifteenth of
that which the "double three legged gravity escapement" offers and so requires
less impulse to keep up the same length of arc of vibration.
Another feature in favour of 90 or more teeth is that this escapement has no
loss through "drop" in fact "drop" has been entirely utilized to lift the gravity
arms. By escaping the pallets over fewer teeth the lifting angle will be increased
to almost any desired extent.
66
"
The 90 or more toothed gravity mechanism (as compared with the 30 toothed of
'Graham") requires no drop," and it has a fixed quantity to unlock whether
the vibrations of the pendulum describe large or small ares Moreover although
I have only two degrees of motion in the 90 toothed wheel or one degree in an
180 toothed wheel I can give more speed to the gravity arms by lessening the
number of teeth over which the pallets escape. This would be desirable when
clocks with short pendulums are provided with gravity escapement.
Now, as the pressure on the locking is inversely proportional to the radius of

page_text: the escape wheel it follows that there can be only one third of resistance to
overcome when the respective sizes of wheels are taken into account, so that
the 90 toothed gravity escapement does not require more than one third of the
weight that the usual 30 toothed Graham escapement has, all other conditions
being the same, viz. the same pendulums and suspension springs, the same are
of vibration, and the same excellency of clock train construction and make.
To recapitulate; In the 90 toothed escapement 2 degrees of train motion are
expended for each beat of the pendulum, in the 30 toothed Graham escapement
6 degrees are expended and in the double three legged gravity escapement 30
degrees of the train motion for each beat of the pendulum are expended.
The escapement wheel in this new escapement being necessarily large it is pre-
ferably planted so as to work outside the pillar plate, close to the pendulum rod as
shewn in Fig. 4. Where space is not available for a long pendulum a horizontal
pendulum may be used or a horizontal and a vertical pendulum may be used in
combination.
Instead of gravity arms as described I may use springs which in case of an
over compensated pendulum give good results.
The gravity escapement made as described will thus be found to possess the fol-
lowing advantages; it requires considerably less weight for driving than the
usual ones, loses nothing in "drop" as it is converted into impulse, unlocks in the
line of centres, gives impulse to the pendulum when most needed, cannot trip and
requires no oil on the pallets, needs no fly to the escape pinion, may advantage-
ously have strong and short club teeth, admits of a clock being made with one
wheel only, which is its own dial such clock being able to go for a year without
winding and with very little driving weight. A clock so made can show time
to the second, whereby it is of special value for frequent time signals along the
coast instead of the time balls that generally give a signal only once in 24 hours
and it can be electrically connected to other clocks. For a giant clock it needs
little correction for temperature if the pendulum is swung in a deep well and
probably none at all when the pendulum rod is made of nickel steel.
Having now particularly described and ascertained the, nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. The application and use in clocks of an escapement wheel of largely increased
diameter having say 90 teeth or more in combination with independently hung
gravity arms which are alternately eased off the pendulum as soon as the latter has
unlocked the tooth of the wheel, the pendulum receiving its impulse by the gravity
of the same arm during its return to the line of centres substantially as set forth.
2. The constructions of gravity escapements described with reference to the
drawings.
3. A giant clock consisting of a six seconds pendulum two gravity arms and
a wheel of such a size as to have say 3600 teeth, said wheel forming the escape-
ment wheel, and the dial so as to dispense with hands, train of wheels and special
dialling substantially as described with reference to Figures 1, 2 and 3.
Dated this Eleventh day (T)
1000
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.