AN IMPROVED ESCAPEMENT FOR CLOCKS AND OTHER TIMEPIECES
Year: 1877

page_text: LETTERS PATENT to Samuel Hughes McClellan, of Deptford, in the County of
Kent, Watchmaker, for the Invention of "AN IMPROVED ESCAPEMENT FOR
CLOCKS AND OTHER TIMEPIECES."
enled the 29th September 1877, and dated the 10th April 1877.
PROVISIONAL SPECIFICATION left by the said Samuel Hughes McClellan at
the Office of the Commissioners of Patents on the 10th April 1877.
SAMUEL HUGHES MCCLELLAN, of Deptford, in the County of Kent, Watchmaker.
"AN IMPROVED ESCAPEMENT FOR CLOCKS AND OTHER TIMEPIECES.'
"
My Invention is applicable to all kinds of clocks and other timepieces, whether
used on board ship or in other places where the clock or timepiece cannot be always
maintained in an upright position, or whether used for house clocks or timepieces
of any kind, as by means of my improved escapement these clocks or timepieces
may be removed from their usual places for dusting or cleaning purposes without
fear of stopping or other disarrangement of parts, as is now the case.
In carrying out my Invention I dispense with the pendulum, and use in place
thereof a balance and hair spring, which are mounted on the upper end of a staff or
shaft. This staff is supported by pivots at right angles to the arbor of the escape
wheel, thus dispensing with the contrate wheel acting in escape wheel pinion, as
heretofore. The staff carries at its lower end a disc which is provided with a pallet
to actuate a device for unlocking the escape wheel. About the middle of the balance
staff, and on a level with the top of the teeth of the escape wheel, is mounted a
second disc also provided with a pallet, against which the teeth of the escape wheel
strike in succession, and thus cause the oscillation of the balance wheel in one
direction, the reverse motion being obtained from the hair spring.
The unlocking device consists of a disc or pallet mounted on a stud or arbor, or
in any other suitable manner at right angles to the arbor of the escape wheel, and
provided with a lever or arm, which lever or arm extends towards the balance staff
or shaft.
A spring is employed to cause the disc or pallet to return to its normal position
after the unlocking of the escape wheel. This unlocking is effected by the pallet or
pin of the lower disc striking as it oscillates with the balance staff against the end

page_text: of the lever, which causes the disc to oscillate on its stud sufficient to release the
tooth of the escape wheel bearing against the disc.
Soon after the release takes place the pallet or pin on the lower disc of the balance
staff passes the end of the lever or arm, and the disc is brought back to its proper
position by the spring ready to stop the next tooth.
The teeth of the escape wheel are made to radiate from the centre instead of
being at an angle, as heretofore; this I effect by drilling the wheel blank, leaving a
club end to the tooth, the object being to obtain strength, and to allow a clear space
for the oscillation of the disc and pallet, or if preferred the teeth may be formed by
means of a suitable punching tool.
In place of the discs and pallets oscillating levers may be employed, and the
escapement is provided with a suitable regulator, the index of which is actuated
through an opening in the dial of the clock or timepiece, and placed under the rim
or bizzle for holding the glass of the case, where it is out of sight when the glass is
closed.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Samuel Hughos McClellan in the Great Seal Patent Office on the
10th October 1877.
SAMUEL HUGHES MCCLELLAN, of Deptford, in the County of Kent, Watchmaker.
"AN IMPROVED ESCAPEMENT FOR CLOCKS AND OTHER TIMEPIECES."
It has hitherto been almost impossible to obtain in common clocks and time-
pieces a perfect "dead beat," which is very essential to a really good timekeeper,
and this difficulty has only been overcome in chronometers and other expensive
clocks and timepieces by an expensive and delicate arrangement of parts.
In clocks and timepieces as usually constructed there is always an amount of
back lash (as the pallets engage with or withdraw from the escape wheel), which is
very detrimental to keeping accurate time. The object of my Invention is to
obviate this objection, and to obtain at a cheap rate a clock or timepiece with a
"dead beat" action, which is so essential to ensure accuracy.
In Sheet I. of the accompanying Drawings I have shown my Invention adapted
to clocks.
Fig. 1 is a front elevation, drawn on a large scale, of a clock constructed according
to my improvements, but with the face plate removed; Fig. 2 is a side elevation of
the same.
Fig. 3 is a top view or plan view, as seen from above.
Figures 4 and 5 are enlarged views in elevation of parts of the clockworks detached;
and Figures 6 and 8 are top views, also enlarged, and corresponding to Figures 4
and 5.
Fig. 7 is another top view, the three Figures G, 7, and 8 showing the varied
positions taken up by the escapement during the stroke.
The same letters of reference correspond to similar parts in all the Figures.
In adapting my Invention to clocks I dispense with the pendulum, and use in
place thereof a balance wheel A, and hair spring A¹. The balance wheel and hair
spring I mount on the upper end of a staff or shaft B, which is supported by pivots
or brackets a, a, at a right angle to the arbor b of the escape wheel C. By placing
the staff or shaft B in the position indicated I am enabled to dispense with the
contrate wheel acting in escape wheel pinion, as heretofore. The staff or shaft B
carries at its lower end a disc c, which is provided on its under side with a pallet d
(set at a right angle to the disc c) to actuate a device for unlocking the escape
wheel C. About the middle of the balance staff' B, and on a level with the top of
the teeth of the escape wheel C is mounted a second and larger disc c. A segment
of this disc c is cut away, see Figures 6, 7, and S, and near the centre of the part left
by cutting away this segment is placed a horizontal pallet f, against which the teeth of

page_text: the escape wheel C strike in succession (as a fresh tooth is released from the locking
device), and propel the balance wheel C in one direction, the reverse oscillation being
obtained from the hair spring A¹, Fig. 3.
The unlocking device consists of a disc or pallet g, mounted on a stud, pin, or
pivots h, carried by a bracket h¹ secured to the back plate of the clock frame, or in
any other suitable manner at right angles to the arbor b of the escape wheel C, and
is provided with a lever arm . The disc or pallet g is cut away on one side and
parallel to the lever or arm to form a shoulder m, which will act as a stop to the teeth
of the escape wheel C, and also when tho disc g is rocked on its stud to allow the
escape wheel C to pass freely.
On the side opposite to the lever or arm i, or in any other convenient part, the
disc or pallet g is cut away to form a shoulder, which abuts against a vertical stop
pin j, firmly secured to the bracket 1, and a spring & which bears against a vertical
pin or stude on the upper side of the disc g is employed to cause the disc or pallet g
to return to its normal position after the unlocking of the escape wheel C.
The lever or arm i, which extends towards and nearly touches the staff or shaft B
of the balance A. (but parallel with, though below, the plane of the disc c on the
lower end of said staff) is formed of two parts, as shown in Figures 6, 7, and 8, vizt.,
a rigid part and a flexible or elastic part, the rigid part being somewhat shorter
than the flexible or elastic part, so that as the staff or shaft B oscillatos in the
direction of the small arrow, Fig. 8, the pallet d on the disc c will clear the rigid
part, and bear against the flexible or elastic part only, and the amount of resistance
to the return oscillation of the staff B to be overcome will thus be reduced to the
minimum, but when the staff or shaft B is oscillating in the direction of the small
arrow, Fig. 6, the two parts will form one rigid arm, the difference in the length
being too slight to allow of any springing of the flexible or elastic part.
A modification of the locking device is shown at Fig. 9, and consists in forming
the lever or arm i of one piece, and instead of cutting away the disc g to form a
shoulder to abut against the stop pin f, as in Figures 7 and 8, which latter is also
dispensed with. I provide two vertical pins l, and so place them upon the upper
side of the disc g that when the disc is in its normal position the spring k shall
bear equally on both pins, but as the disc g is rocked on its stud pin in either
direction the spring will bear alternately on each of the pins 7.
I will now proceed to explain the working of the escapement. Let it be supposed
that the clock is wound up, the strain of the spring or weights will then be upon
the escape wheel C, tending to drive it forward in the direction of the large arrows,
and when in its normal position a tooth will be always bearing against the under
side of the disc or pallet g, as shown at 1*, Fig. 4. Now let the balance A be set in
motion in the direction of the small arrows, Figures 6 and 7, the pallet d of the
disc c will be caused to press against the lever or arm i of the disc or pallet g, and
cause this latter to rock on its stud pin or pivots / sufficiently to allow of the escape
of the tooth 1*. At the same time the pallet f (which is suitably set on the staff
or shaft B for the purpose) of the disc e is brought into position to receive the
tooth 2* (Figures 5 and 6), of the escape wheel C, which by the impetus given by
the spring or weights drives the pallet f forward into the position shown at Fig. 7.
While this is taking place the pallet & passes the end of the lever or arm i of the
pallet g, and allows this latter to regain its normal position, being assisted thereto
by the spring K, and it is thus ready to receive and stop "dead" the next tooth
(say, 3*) of the escape wheel C. By this time the power obtained by the winding-
up of the hair spring A' is brought to bear, and the balance A is caused to oscillate
in the opposite direction (see Fig. 8) until the pallet & passes the end of the elastic
part of the lever or arm i, when sufficient power will be gained by the unwinding
of the hair spring A¹ to cause the return oscillation of the balance A, and the
unlocking and other motions will proceed as before described.
By the above described arrangement of the parts of my improved escapement I
am enabled to obtain a perfect " dead beat," and consequently secure at a very slight
cost an accurate timekeeper.

page_text: The escapement is provided with a regulator D, the index of which is actuated
through an opening in the dial of the clock or tiinepicce, and so placed under the
rim or bizzle for holding the glass of the case as to be out of sight when the glass is
closed.
In order to obtain greater strength in the teeth of the escape wheel C, and also
to allow sufficient space for the free oscillation of the disc e and its pallet I make
the teeth so that they radiate from the centre of the wheel (see Figures 4 and 5)
instead of at an angle, as heretofore. I effect this by drilling the wheel blank,
taking the centre of the circle to be drilled at such a point as will leave a club end
to each tooth, or the teeth may be formed by means of a suitable punching tool.
In Sheet II. of the Drawings I have shown my improved escapement as adapted
to watches, Figures 1ª, 2, and 3ª being plan views, showing the various positions
of he parts during the stroke of the balance wheel; and Fig. 4, a side elevation.
All the parts in these Figures are similarly lettered to the like parts in Sheet I.,
and the action corresponds to that already described for clocks in reference to
Figures 6, 7, and S, and it will not therefore be necessary to further explain the
movement. Slight modifications however occur with regard to the discs and pallets,
such modifications being required to adapt the principle to pocket timepieces, the
most important of these modifications being the use of a pin or pallet m on the disc
g, Figures 1, 2, 3, and 40, Sheet II., in place of the shoulder in on the disc f
Figures 6, 7, 8, and 9, Sheet I., and the relative positions of the escape wheel and
balance staff will be changed to suit the altered circumstances.
All the other modifications required are clearly shown in and will be readily
understood on reference to the Drawings.
I would here remark that I do not intend to confine myself to the exact form of
discs and pallets above shown and described, as they are capable of various modifi-
cations without departing from the principle of my Invention,
Having now described the nature of my improved escapement for clocks and
other timepieces, and having explained the manner of carrying the same into effect,
I wish it to be understood that under the above in part recited Letters Patent I
claim,―
The general construction and arrangement of parts forming my improved escape-
ment, whereby I am enabled to obtain a perfect dead beat, as herein set
forth.
I claim particularly the combination of the disc g and its accessories, with the
parts c and c, and the escapement wheel C, as and for the purpose herein set
forth.
In witness whereof, I, the said Samuel Hughes McClellan, have hereunto set
my hand and seal, the Tenth day of October, in the year of our Lord One
thousand eight hundred and seventy-seven.
SAM¹. H. MCCLELLAN. (L.S.)