IMPROVEMENTS IN CONTINUOUS ROTARY 'SERVO-MOTORS,' AND IN THEIR APPLICATION FOR WORKING SHIPS' RUDDERS, CAPSTANS, HOISTS, CRANES, AND OTHER MACHINERY
Year: 1875

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention
of "IMPROVEMENTS IN CONTINUOUS ROTARY 'SERVO-MOTORS,' AND IN THEIR
APPLICATION FOR WORKING SHIPS' RUDDERS, CAPSTANS, HOISTS, CRANES,
AND OTHER MACHINERY."-A communication from abroad by Farcot
and Sons, of St. Ouen (Seine), and Stapfer de Duclos and Company,
of Marseilles, both in France.
Scaled the 19th April 1876, and dated the 4th November 1875.
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 4th November 1875.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN CONTINUOUS ROTARY 'SERVO-MOTORS,'
AND IN THEIR APPLICATION FOR WORKING SHIPS' RUDDERS, CAPSTANS, HOISTS,
CRANES, AND OTHER MACHINERY," to be as follows:-
This Invention relates to improvements in servo-motors having con-

page_text: tinuous rotary motion, and comprises improvements in their constitutive
arrangement, and in their various applications for working ships'
rudders, capstans, winches, hoists, cranes, and for other purposes.
The Invention consists, 1st, in novel arrangements of controlling gear,
in which a shifting eccentric is employed and operated through the
medium of differential gearing.
Figures 1 and 2 of the accompanying Drawings show one arrangement
of the apparatus.
In constructing the controlling gear of servo-motors it is generally
necessary to place at the disposal of the attendant an angular motion of
considerable extent in order that the attendant may more easily move
the slide valves from the stop point or position of no motion (which is
the mid-point of their course) to either end of their course.
The improved arrangements to be herein-after described afford all the
facilities desirable in this respect.
In Figure 1 a, a¹, a", a¹¹¹, is a cranked driving shaft similar to those
of the servo-motors of this kind described in former Patents, No. 2635,
1872, and No. 1934, 1874. a, driving crank; a', journal bearing;
a", axis of shifting eccentric b for operating the slide valves, to which
it is connected by the ordinary straps c, c', and connecting rods;
d, toothed wheel mounted on the prolongation a" of the driving shaft,
connected to the eccentric by a lug n on the latter, received between
two similar lugs on the face of the wheel. On the portion a" of the
shaft is also mounted differential gear for controlling the eccentric, and
consisting of a wheel floose on axis a, and turned by hand or by an
endless chain, toothed or other gear applied to its periphery. Upon one
of the arms of wheelf there is mounted an axis h, on which turns two
planet pinions e, m, of unequal diameter, which are formed or connected
together, and which gear respectively with spur wheels d and g, also of
unequal diameter, the latter being a wheel keyed on the extreme end of
axis a, the whole being arranged as described in order to shift the
position of eccentric b, and thereby to govern the motor; it is simply
necessary to rotate the wheel ƒ cither way (in the direction of the
arrow 1 for example, the direction and the degree of angular motion
relatively to shaft a, a, being immaterial), whereupon the two planet
pinions m, e, will be carried round to a corresponding extent, and will

page_text: at same time be revolved upon their axes in consequence of the
pinion m gearing with the stationary wheel g.
It will be evident that the degree of angular motion transmitted by
the wheel to the pinions e, m, will be proportionate inversely as the
radii of the wheel and pinion g, m. The pinion e turning in the same
direction (indicated by the arrow 1) as m would not impart any motion
to wheel & upon shaft a, a, if the diameters of d, e, were the same as
g, m, but as e for example is smaller than m, and a larger than g, a
tooth of e in gear with d will move with a less velocity in the direction
of 2 than the corresponding tooth of m, consequently the angular
movement of wheel transmitted to shaft will not as regards wheel d
and its pinion e be entirely compensated by the backward rotation of c
upon, as in the case with m, g; the teeth of 9 will thus for ono
revolution of m, e, on h be moved forward in the direction of 1 or of 3,
a linear amount equal to the difference of the circumferences of e, m, or
of 9, d. It may be said that throughout the angular movement of
wheel the velocity of a point of contact y of the circumference of e
with that of d, and consequently the tangential velocity of d is the
geometrical resultant of the velocity with which the wheel is turned
relatively to axis a, measured at a distance a¹¹¹, y, from axis a, and of
the relative velocity of the circumference of pinion e with respect to the
system of comparison f, which is supposed to be stationary. These two
velocities being in opposite directions, if equal, would neutralize each
other, and wheel & would remain stationary, but if unequal, wheel d
will have relatively to wheel fa backward angular motion, either greater
or less than the absolute forward angular motion of wheelf, or relatively
to axis a an angular movement in the same or opposite direction to f,
according as the radius of pinion e is less or greater than that of m.
The extent of this absolute movement of wheel d in one or the other
direction will morcover be greater, as the difference in the radius of m
and e is greater.

page_text: The action of this differential movement may also be otherwise
explained from a geometrical point of view by simply considering
that a force imparted to shaft in the direction 1, for example, will
tend at each clementary movement to turn a line h, y, x, around x as
centre of rotation, and that point / carried around axis a will incline
said line h, y, x, and bring point y to y¹ in the manner of a lever in
turning h, y, x, upon x.
The ratio of the lever arms h, x, y, x, is that
of the radius h, x, of pinion m to the difference y, x, of the radius of m
compared to that of e.
An attentive examination of this apparatus will show its identity in
principle with those described in the former Letters Patent above
referred to. As an evidence of this it is sufficient to observe what
takes place if the motor continues its motion after the attendant has
arrested the hand wheel f. For this purpose it is necessary to consider
not the absolute velocities but the relative angular velocities of the
eccentric and the motor, thus it will be seen that point y which has
been brought by the action of the attendant to y' tends, by its absolute
motion, to pass still further, when, the hand wheel being stopped, the
motor continues its motion in the original direction; but it will also
be observed that during this time the driving crank is moving also in
the same direction, and with an angular velocity greater than that of
the eccentric. The angular distance of the crank and of the eccentric
thus gradually diminishes, and it may be readily demonstrated by a
diagram or algebraically that in reality the latter returns to the position
of no motion at a velocity equal to that which it moved in the opposite
direction. If g were larger than d the effect of rotation on d would.
be produced in the inverse direction to the angular movement imparted
to f.
The arrangement and proportions of the apparatus may be varied
according to circumstances.
• Figures 3 and 4 show an arrangement similar to the foregoing which,
although applicable only for shifting an ordinary eccentric, and con-
sequently possessing some disadvantage as regards precision of working,
may in certain cases and according to circumstances be found more
simple in arrangement and equally useful.
An arrangement of differential gearing is employed similar to that
shown in Figures 1 and 2, except that the wheel g is larger than d, and

page_text: that consequently when the attendant actuates the hand wheelf in the
direction of the arrow 1 the wheel d is moved in the reverse direction,
indicated by the arrow 3. The wheel dis attached to an ordinary
eccentric b which shifts about a centre coinciding with the axis of the
driving shaft a', a", a", which carries the crank as The eccentric 6 is
represented in its mid position, that is to say, its truc centre is in line
with the crank a and diametrically opposite thereto. It will thus be
seen at once that the rotation of d in the direction of the arrow 3 will
cause point to pass to 1, Figure 4, that is to say, into a suitablo
position for the rotation of the driving shaft in the direction of arrow 1.
It will also be seen that if the attendant stops the hand wheel
wheel in continuing its motion will carry d with it in the same
direction by means of the planet wheels m and e, and will cause
point to retrograde to and then to ". In this manner a control
is exercised, but the angular extent of the position of no motion will
be relatively large, that is to say, from about z¹ to ", and the precision
of the control will be not nearly so great as when the shifting eccentric
is mounted to turn on a special crank axis.
the
As shown in another arrangement illustrated in Figures 5, 6, & 7,
an eccentric turning on a special axis may be employed, even where
the pinion m is smaller than e, in which case, as previously explained,
the direction of motion of d will be reversed. In this instance the
following arrangement is adopted :-Between the wheel & which turns
in the reverse direction to f and eccentric 6 is placed an intermediate
connection consisting, for example, of a frame i working up and down
upon the shoulder ; of the shaft, and by which it is guided. On the
wheel is placed a stud which moving therewith in the direction
of the arrow 3 carries with it the frame in an upward direction for
example, Figure 7, and thereby moves also in an upward direction
another stud fixed on the eccentric b. These two studs are furnished
with sliding blocks working in lateral slots formed on the frame i. It
will be readily seen that the rotary motion imparted in the direction
of arrow 3 will thus be transmitted in the inverse direction 4 to the
eccentric 6 by the agency of the frame and the studs, 21, and con-
sequently the rotation of the motor will be also reversed in the
direction 4, as also that of g. If now it be supposed, as above, that
the attendant who has moved the machine in the direction 1 stops, and
that the motion of the motor transmitted to in the direction 4 or 1

page_text: continues, the point h will become stationary as before, but the impulsion
of g in the direction 4 (Figure 5) will reverse the angular motion that
the attendant had imparted to m in the direction of 2, and consequently
the apparatus will be under the required control. The same result
might be obtained by substituting for frame i any other intermediate
connection; for instance, by means of a bevel pinion having its axis
normal to the line a', a¹¹, and gearing with two wheels mounted laterally
one on d and the other on b. In this way any other arrangement might
be operated.
Figures 8, 9, and 10 illustrate another modification. The importanco.
has already been mentioned of the optional amplification of the angular
movement placed at the disposition of the attendant to enable the diş-
tributing slide valves or other controlling organ to be shifted with less
power, and the arrangements above described give in this respect all the
latitude of variation that may be desired by the employment of a
differential movement.
I will now describe another arrangement which within practical and
ordinary limits may also be advantageously employed for obtaining the
same result, that is to say, the amplification of the angular movement
of control in the hands of the attendant.
In Figures 8, 9, and 10, the parts and details designated a, a¹, a¹¹, b,
c, c', in the preceding Figures are reproduced; a" is again the pro-
longation of the driving shaft; j, a plate forged on this shaft and
separating the eccentric 6 from the wheel d by which it is operated;
n, connecting stud by which the wheel d carries with it the eccentric b.
In front of the platej is placed a support or bearing k connected to j by
bolts 8, 8, 8, or otherwise. This bearing receives shaft 7 by which the
attendant moves and controls the motor by means of wheel f. The
shaft carries a pinion 7 gearing with a wheel m, which is in one with
the pinion e of the wheel d; m, e, are mounted on and have bolt & for
their axis. It will be readily understood on examining the figures that
the angular motion of wheel fis by these arrangements considerably
amplified relatively to that of wheel d and to the shifting of band will
be generally more than sufficient. This arrangement therefore con-
stitutes a practical and satisfactory solution of the problem given. As
it may happen that the useful effect produced by this system of gearing
may be relatively high, and that in consequence the total amount of

page_text: 2
friction may be insufficient to prevent all back lash or recoil under the
variable resistance of the eccentric b, a flat washer is placed on shaft
between the bearing k and the wheel f, and on the same squared part of
the shaft as f, and between this washer and ƒ an elastic washer ≈'.
The bearing is thus pressed by the washer 2' between the shoulder of
shaft and the washer z. By means of a nut f', the pressure may be so
regulated as to produce the additional friction necessary to ensure the
requisite stability of the apparatus. This completes the arrangement
which it is believed will be of considerable service in many cases.
Figure 11 shows another arrangement. a, driving shaft; b, shaft
communicating the shifting movement to the eccentrics of the dis-
tributing slide valves, or to any other controlling organ used; d, hand
wheel operated by the attendant; c, screw working through the wheel d
at a certain distance from the centre of shaft a, and turning around the
latter by the rotation of wheel d; f, toothed wheel keyed on shaft a;
9, pinion gearing therewith and keyed on screw e; h, skew wheel keyed
on shaft ; and k, skew pinion keyed on screw e and gearing with h.
The ratio of wheels f, g, is the same as that of wheels k, k.
It will be readily seen that by turning wheel d in one or other
direction an angular movement will be imparted to shaft b, which move-
ment may be as small as may be desired for a large angular movement
of wheel d. The wheel d in turning carries with it the two planet
pinions g, k, and if these two pinions had straight teeth they would of
course merely roll around their respective wheels without producing any
angular movement of the wheel h relatively to f, their ratios being equal,
but the pinion g in rolling around the wheelf, which is fixed, turns the
screw e in its nut, which is part of the hand wheel, there is therefore a
longitudinal movement of the screw e and of the two pinions g and k
relatively to the wheel d. The effect of this longitudinal movement is
that the pinion k having skew teeth imparts to the wheel / in one
direction or the other, according to the direction of the tangent to the
teeth, a small angular movement which is proportionate to the
inclination of the teeth, and which effects the shifting of the eccentrics
or of the distributing valves or other controlling organ employed, this
effect being produced by an angular movement of the wheel d, as great
as may be desired and determined by the proportions of the wheels, the
pitch of the screw e and the inclination of the teeth of the skew wheels
hand. This method of amplifying the movement is another means

page_text: which may be serviceable in many cases, and may be varied in
arrangement and detail according to requirements.
Figure 12 shows a modification of the mode already described of
employing gear wheels for amplifying the angular movement for
shifting the eccentric, or for operating any other controlling apparatus.
In this modification bevel wheels are employed which have the
advantage of amplifying the angular movement at the disposition of
the attendant to as great an extent as may be desired in practice, so that
less effort will be required to reverse the slide valve or other controlling
organ. The attendant by turning the wheel which is mounted loose
on the end of the driving shaft, transmits to the eccentric b through
stud n and toothed gear g, m, c, d, an angular movement in the same
direction but slower than that of f. In this manner the eccentric is
shifted upon its eccentric axis a" in the direction required for turning
the crank the same way as the wheelf. If the movement of wheels
fand g be then arrested, shaft a', a", which continues to revolve carries
with it spindle e, h, and wheels m, e; wheel m in moving around pinion
receives rotary motion about its axis which is transmitted to wheel d
by pinion e. It will thus be seen that wheel d will receive a compound
rotary motion composed of a movement in the same direction, and of the
same angular amount as that of the crank by the operation of pinion e
acting as a carrier, and another movement in the opposite direction and
of less angular amount transmitted by the same pinion e, and due to the
rotation of wheel mon pinion g, the result of the combination of these
two movements is a rotary motion in the same direction as that of the
crank, but of less amplitude, so that the eccentric will be soon overtaken
by it, and will consequently return to the position of no motion. The
wheel d is made in two parts loose on the axis, and has a flange around
its periphery to which is bolted a cover enclosing the gear. The
spindle e, h, turns in a bearing on the motor shaft; dished elastic
washer regulated by a nut f', which together with the flat washer =
ensures sufficient friction upon the hub of wheelf to prevent all back
lash under the varying resistance of eccentric b.
It may be objected that in the planet motion arrangements of con-
trolling apparatus described and shown in Figures 1, 2, 3, and 4, the
two forces applied in contrary directions at the points of contact of
the wheel and pinion gear g, m, and d, e, will tend to produce a torsion
on the band wheel which supports spindle h, and it is possible that

page_text: under certain circumstances the great friction between the gears or
on their axes would render such arrangements difficult of employment.
Figures 18 and 19 show a modification of the above described arrange-
ments of controlling gear, by which all tortion and loosening of the
hand wheel is entirely avoided, without however sacrificing the
advantages of simplicity and efficient action possessed by such arrange-
ments. To this end the spindle of the planet pinions is supported at
each end in two bearings carried by a circular casing f' fixed to the
hand wheel, or, as in the particular instance illustrated, to a pinion ƒ
substituted for the hand wheel. The casing f¹ completely encloses the
whole of the planet gear which is made as small as possible, and is
secured from tortion or displacement by a bearing upon the extension a*
of the shaft, and another on a circular collar formed on the movable
wheel d. The action of the apparatus is in other respects the same as in
the former arrangements, as may be seen by comparing the Figures.
It will be observed that the motion is in this case supposed to be
transmitted to the apparatus from the hand wheel by an endless chain
in gear with a pinion i; on the axis j of this pinion is keyed a wheel k
which gears with the pinion f fast with the casing f'. The diameter of
wheel kis large in proportion to that of pinion f, in order to reduce the
number of revolutions which is generally considerable, to be imparted
by the hand of the attendant. This arrangement is especially useful
for apparatus of small dimensions, and operated directly, in which case
the hand wheel would be keyed on shaft j.
Another advantage attending the use of this intermediate shaft when the
apparatus is employed in ships of war, is that the motion may be reversed
for turning the servo-motor windlass working the rudder in the same
direction as the hand steering wheels, the direction of motion of the band
wheel remaining the same as usual. Morcover in order, in this particular
application to rudders, for example, to prevent the tiller from moving
beyond its due limits, and striking against the sides of the ship, it is
necessary to limit the number of turns of the hand wheel or the machine
in one direction or the other. For this purpose the axis j is screw
threaded and by its rotation causes a nut 1, which is prevented from turn-
ing by the cross bars m³ to travel along it. After a certain number of
turns the nut arrives at the end of its course, and presents itself in the
path of one of the lugs p, p', mounted on wheel k and pinion i respec-

page_text: tively, whereupon the motion of the hand wheel is arrested, and conse-
quently that of the machine.
Figures 20 and 21 show a simplified arrangement of controlling gear,
in which a spiral sleeve is employed, such as described in a former
Patent granted to me, bearing date June 3rd, 1874, No. 1934. f is the
driving shaft with a cranked part 8, on which is mounted the eccentric n
with its two straps i, i. Besides the spiral ; formed on the prolongation
off, there is also a screw j, on which works a nut and pinion / operated
by any one of the means before described. The sleeve m, described in
the said former Patent, is also used in this case, and is caused to par-
ticipate in the traversing movement of nut to which it is connected
by a flange m, but the long pitched spirals formed on its exterior
in the former case, which by turning the socket n¹ shifted, the
eccentric n are now formed on the interior of the sleeve m, which thus
forms a nut working on the spirals j, j³, on screw j and intersecting
the shorter pitched screw j. Thus it will be readily seen that any
difference of velocity in the rotation of pinion and driving shaft ƒ will
cause the sleeve m to traverse along the extension of the shaft, and at
same time by working in the spirals j, j³, to receive a slight rotary
motion which is transmitted to the eccentric n through rod n', whereby
the eccentric is shifted as desired the same as by the socket n' in the
former Patent referred to.
It will be remarked that in Figures 20 and 21 the pinion is operated
and controlled in a similar manner to that described with reference to
Figures 18 and 19 as regards the limitation and regulation of its motion.
The pinion is made of sufficient breadth to gear constantly during its
traverse with the wheel by which it is operated.
The Invention further relates to improvements in the continuous
rotary servo-motors described in the said Patent before referred to, in
which a variable normal lead and partial expansion are obtained by
means of a shifting eccentric turning upon a crank axis, the true centre
of the eccentric itself moving in the arc of a circle passing through the
centre of rotation of the main or driving shaft.
Figure 18 shows a general view of this apparatus with the present
improvements, which are applicable not only to this apparatus in its
various applications, but also to other similar. apparatus. a, a¹, steam

page_text: cylinders (other liquid or gaseous fluid may be used) inclined towards
one another at an angle of 90°; their pistons will be designated by b, b' ;
c, c', piston rods; and d, d, connecting rods; e, e', guides; f, shaft
cranked at ; f¹, counterpoise for moving parts of the machine;
9,9', valve chests, the slide valves contained therein being designated h, h';
i, i¹, eccentric rods; n, shifting eccentric turning on the cranked portion s
of shaft f. The shifting of the eccentric is effected by either of the
methods described; that shown in Figure 13 is the same as in the
previous Patent, and it is therefore unnecessary to again describe it; but
the method shown in Figures 1 and 2 might be employed equally well,
or that shown in Figures 8, 9, and 10, which is represented as applied
for this arrangement in Figure 12, or that shown in Figures 3 and 4, or
that shown in Figures 18 and 19 might be used. The rotation of shaft ƒ
is transmitted by pinion p and wheel p' to the drum which carries tho
windlass to be operated. When the servo-motor windlass is employed
for raising weights or for any analogous purpose the wheel p' may
without inconvenience be keyed directly on shaft q; but for certain
particular applications, for example for working rudders, it is necessary
to provide against the servo-motor or its conucctions being rendered
unserviceable by an accident, when it would be necessary to work the
rudder temporarily by hand.
In the machine shown provision is made for such an event by an
arrangement which may be used with advantage in other similar
circumstances. The drum r on which is wound the tackle for working
the rudder is caused to turn with shaft q by means of a key which
allows the drum to move longitudinally along the shaft. This longitudinal
movement is imparted by a hand wheel and screw ¹ working through
a nut, and connected to a cross bar ² fixed in the drum rº,
and passing
through a slot in shaft q. At the ends of the drum are clutches geared
at will with either of two other clutches, of which one is on wheel p¹,
and the other on pinion a. This pinion is loose on shaft q, as likewise
wheel p', and it is geared by a pitch chain with the hand steering
wheels, by which the rudder is worked in case of accident to the servo-
motor. It will thus be seen that the hand can be readily substituted for
the steam steering gear, or vice versa; suppose the drum to be in the
position, Figure 13, in gear with wheel p', and operated by the servo-
motor; in this case the barrel of the aft steering wheel is locked, and
serves as a purchase for the drum for working the tackle.

page_text: if it be desired for any reason to steer with the wheel on the bridge
geared by a chain with pinion x, it is only necessary to put drum in
gear with pinion by working screw, the barrel of the aft steering
wheel serving always as a purchase. If on the other hand it is desired
to steer with the wheel aft the drum must be prevented from turning,
so that it may act as a purchase for the aft wheel. For this purpose it
would be geared again with wheel p', and the latter would be locked by
means of a bolt fitted in the frame of the machine, and passing between
the teeth of the wheel. These changes may be effected with the
greatest rapidity so that the working of the rudder is not appreciably
interrupted.
To prevent the coils of the chain wound on drum riding one upon
another, the chain is passed over a double pulley o mounted on a
carrier on a screw shaft of, along which it is caused to traverso
simultaneously with the winding of the chain upon the drum by the
rotation of said shaft which is geared with and receives motion from the
drum by an endless chain and chain wheels. By this means the chain
is always guided on to the part of the drum on whiich it should be
wound, and all riding of the coils on one another is prevented.
In certain cases, as for example, that of an engine working at a
comparatively low speed, it may happen that an extent of angular
motion not exceeding a fraction of a turn may suffice to ensure the
requisite precision of working. Figures 22 and 23 show an arrange-
ment adapted for this particular case, in which the attendant acting on
the circumference of a large hand wheel shifts the eccentric directly
through the medium of pin u¹, the extent of motion being from about
150 to 160 degrees.
The arrangement shown in Figures 24, 25, and 20 may also be
employed, preferably, in merchant vessels. a, main driving shaft made
hollow throughout its length; b, shaft working inside of shaft a, by a
which the attendant, placed at one end of the engine, may adjust the
eccentrics at the opposite end; c, crank pin on shaft b; d, rock shaft
traversing the main crank f, and operated through an arm d' keyed
thereon from the crank pin c of shaft b. The shaft d has at its other
end a crank arm ", and pin ", by which the slide valve rods are
worked.
It will be readily understood, as shown in the diagram. Figure 26.

page_text: that the attendant by rotating shaft 6 in one or other direction shifts the
position relatively to the main crank of the crank pin d, which operates
the valve rods, and thus controls the operation of the engine. The crank
pin c being fixed at a short radius from the axis of shaft b it will be seen
that the attendant operating this shaft will have at his disposition an
extent of movement equal to 180°. These arrangements may be varied
at will, according to circumstances. The hand wheel may be made suffi-
ciently large to overcome with case the resistance of the valves. By
means of suitable connections the fly wheel may be used for steering by
hand.
Figures 15, 16, & 17 relate to the conjugation or controlling by one
attendant of an assemblago of servo-motors having continuous rotary
motion, or of servo-motors having continuous rotary motion and others
having alternate or other motion. This conjugation, in accordance with
the principle enunciated, is effected by means of abscisses and of various
ordinates or co-ordinates upon various planes of projection or in space.
It is evident that these co-ordinates might be delineated or defined upon
surfaces of different kinds, plane, cylindrical, conical, or irregular ;
these co-ordinates might be convergent or non-convergent, &c., the
principle upon which the conjugation of servo-motors is effected being
always to assemble in one point the centre of general direction the
various respective trajectories or representative paths of the translation
to be effected by each servo-motor, in order to construct therewith in
space a total resultant trajectory, which defines and completely controls
the ensemble of the movements of the apparatus operated, and which
may not be similar to any one of the partial trajectories respectively
described in accordance with each co-ordinate.

page_text: -
The arrangement to suit the particular case in question may be as
follows: Hand wheel a is mounted on a sleeve a' capable of sliding in
bearing a" and upon shaft b. The shaft bis made square or has a keyway,
so that a' and 6 may revolve together, and also slide one on the other
longitudinally. The sleeve a' is grooved at a to receive a collar, by
which in moving along shaft it acts upon the end of a bell-crank
lever d, d', or other device controlling the second servo-motor.
It will be at once evident that the attendant, both whilst turning or
holding the hand wheel stationary, may move it to and fro, together
with sleeve a', and that in this way any point on the hand wheel, for
example, on the periphery or handle c, or other point on which the
attendant acts, will constitute this centre of general direction for the
translation of the object operated according to two co-ordinates for con-
trolling two servo-motors. For example, heavy artillery may in this
manner be trained horizontally by means of hand wheel a, and elevated
or depressed by lever d, d'.
The training of a heavy gun mounted on a small gun boat may also
be performed by the above means, a being used for working the rudder,
either with the aid of a servo-motor or by screw or other gearing, and
d, d', for elevating or depressing it through the medium of a steam,
hydraulic, or other servo-motor.
It is evident that if by a suitable arrangement a third co-ordinate be
established by a third and distinct transmission of the rotation of a, and
the longitudinal traverse of a', a third law or trajectory distinct from
the two first would be created, in accordance with which the point or
centre of general direction will control the apparatus, as in the two
former cases. Similarly for an indefinite number of co-ordinates and of
servo-motors, in accordance with the Specification of a former Patent,
granted September 4th, 1872, No. 2635, the arrangement illustrated may
be placed either horizontally, vertically, or at any desired angle of shaft b.
These means may be adopted for coupling a servo-motor with a motor not
so controlled or other mechanism, or for connecting two mechanisms
together, whether operated by hand or otherwise, as, for example, for
working small guns on board of torpedo boats. The same combined
movements may also be used for actuating gearing of any kind, such as
of auxiliary servo-motors.
Bicure 17 shoves another example of the method. of coupling twea

page_text: servo-motors having continuous or non-continuous rotary motion, the
same being applicable for training great guns, and other purposes; m,
n, horizontal and vertical connecting rods jointed together at x. Con-
necting rod m is also jointed to a lever p, and rod n to lever q, the said
levers being mounted in any suitable plane, or replaced by other con-
nections or means of governing the controlling gear of each servo-motor.
It will be at once seen that x is the centre of general direction, which
on being moved horizontally oscillates lever p for training the gun,
while on the other hand by rising a lever q will be operated vertically
for elevating or depressing the gun. If point x be shifted more or less
obliquely, the two movements may be combined together under the
control of the gunner who lays the gun.
SPECIFICATION in pursuance of the conditions of the Letter Patent,
filed by the said Alexander Melville Clark in the Great Seal
Patent Office on the 3rd May 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lanc, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourth day of November, in the
year of our Lord One thousand eight hundred and seventy-five, in
the thirty-ninth year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Alexander Melville Clark,
Her special license that I, the said Alexander Melville Clark, my
executors, administrators, and assigns, or such others as I, the said
Alexander Melville Clark, 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 and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN CONTINUOUS ROTARY SERVO-
MOTORS, AND IN THEIR APPLICATION FOR WORKING SHIPS' RUDDERS, CAPSTANS,
HOISTS, CRANES, AND OTHER MACHINERY," a communication to me from abroad
by Farcot and Sons, of St. Ouen (Seine), and Stapfer de Duclos and

page_text: the slide valves, to which it is connected by the ordinary straps c, c¹,
and connecting rods; d, toothed wheel mounted on the prolongation a
of the driving shaft, and connected to the eccentric by a lug n on the
latter, received between two similar lugs on the face of the wheel. On
the portion a of the shaft is also mounted differential gear for con-
trolling the eccentric, and consisting of a wheel floose on axis all, and
turned by hand or by an endless chain toothed or other gear applied to
its periphery. Upon one of the arms of wheelf there is mounted an
axis h, on which turn two planet pinions e, m, of unequal diameter,
which are formed or connected together, and which gear respectively
with spur
wheels d and g, also of unequal diameter, the latter being a
wheel keyed on the extreme end of axis a, the whole being arranged
as described in order to shift the position of eccentric b and thereby to
govern the motor, it is simply necessary to rotate the wheel fcither
way (in the direction of the arrow 1, for example, the direction and the
degree of angular motion relatively to shaft a, a being immaterial)
whereupon the two planet pinions m, e, will be carried round to a
corresponding extent, and will at same time be revolved upon their
axis in consequence of the pinion m gearing with the stationary
wheel g.
It will be evident that the degree of angular motion transmitted by
the wheel to the pinions e, m, will be proportionate inversely as the
radii of the wheel and pinion g, m. The pinion e turning in the same
direction indicated by the arrow 1 as m would not impart any motion
to wheel d upon shaft a, a", if the diameters of d, e, were the same as
g, m, but as e for example is smaller than m and d larger than g a tooth
of e in gear with d will move with a less velocity in the direction of 2
than the corresponding tooth of m, consequently the angular movement
of wheel transmitted to shaft will not, as regards wheel d and its
pinion e, be entirely compensated by the backward rotation of e upon h,
as is the case with m, g; the teeth of g will thus for one revolution of
m, e, on h be moved forward in the direction of 1 or of 3, a linear
amount equal to the difference of the circumferences of e, m, or of g, d.
It may be said that throughout the angular movement of wheel the
velocity of a point of contact y of the circumference of e with that of
d, and consequently the tangential velocity of d, is the geometrical
resultant of the velocity with which the wheel f is turned relatively to
axis a, measured at a distance a¹¹, y, from axis a, and of the relative
B

page_text: velocity of the circumference of pinion e with respect to the system of
comparison f which is supposed to be stationary. These two velocities
being in opposite directions, if equal, would neutralize each other, and
wheel d would remain stationary, but if unequal wheel a would have
relatively to wheel a backward angular motion either greater or less
than the absolute forward angular motion of wheel f, or relatively to
axis a an angular movement in the same or opposite direction to f,
according as the radius of pinion e is less or greater than that of m.
The extent of this absolute movement of wheel d in one or the other
direction will moreover be greater as the difference in the radius of m
and e is greater.
It will be readily conceived that in this manner the angular move-
ment imparted to f may be reduced as much as desired in its transmission
to d or to the eccentric b, and that consequently the power to be applied
to the periphery off will be so much the less, as the angular movement
of d is reduced, relatively to that off, regard being also had to the
difference of radius.
The action of this differential movement may also be otherwise
explained from a geometrical point of view, by simply considering that
a force imparted to shaft h, in the direction 1 for example, will tend at
cach elementary movement to turn a line h, y, a, around x as centre of
rotation, and that point carried around axis a will incline said
linc h, y, x, and bring point y to y' in the manner of a lever in turning
h, y, a, upon a. The ratio of the lever arms h, x, y, x, is that of the
radius h, x, of pinion m to the difference y, x, of the radius of m com-
pared to that of c.
An attentive examination of this apparatus will show its identity_in
principle with those described in the former Letters Patent above
referred to. As an evidence of this it is sufficient to observe what takes
place if the motor continues its motion after the attendant has arrested
the hand wheelf. For this purpose it is necessary to consider not the
absolute velocities, but the relative angular velocities of the eccentric
and the motor, thus it will be seen that point y which has been brought
by the action of the attendant to y¹, tends by its absolute motion to
pass still further, when the hand wheel being stopped, the motor con-
tinues its motion in the original direction'; but it will also be observed
that during this time the driving crank is moving also in the same

page_text: direction and with an angular velocity greater than that of the cocentric.
The angular distance of the crank and of the eccentric thus gradually
diminishes, and it may be readily demonstrated by a diagram or
algebraically that in reality the latter returns to the position of no
motion at a velocity equal to that at which it moved in the opposite
direction. If 9 were larger than d, the effect of rotation on a would
be produced in the inverse direction to the angular movement imparted
The angular distance of the crank and of the cccentric thus gradually
diminishes, and it may be readily demonstrated by a diagram or
algebraically that in reality the latter returns to the position of no
motion at a velocity equal to that at which it moved in the opposito
direction. If g were larger than d, the effect of rotation on & would
be produced in the inverse direction to the angular movement imparted
to j
The arrangement and proportions of the apparatus may be varied
according to circumstances.
Figures 3 and 4 show an arrangement similar to the foregoing, which
although applicable only for shifting an ordinary eccentric, and conse-
quently possessing some disadvantage as regards precision of working
may in certain cases and according to circumstances be found more
simple in arrangement and equally useful.
An arrangement of differential gearing is employed similar to that
shown in Figures 1 and 2, except that the wheel g is larger than d,
and that consequently when the attendant actuates the hand wheelf
in the direction of the arrow 1 the wheel dis moved in the reverso
direction, indicated by the arrow 3. The wheel d is attached to an
ordinary eccentric 6, which shifts about a centre, coinciding with tho
axis of the driving shaft a', a¹, a", which carries the crank a. The
eccentric is represented in its mid position, that is to say, its true
centre is in line with the crank a and diametrically opposite thereto.
It will thus be seen at once that the rotation of d in the direction of
the arrow 3 will cause point to pass to ¹, Figure 4, that is to say,
into a suitable position for the rotation of the driving shaft in the
direction of arrow 1. It will also be seen that if the attendant stops
the hand wheel f, the wheel g in continuing its motion will carry & with
it in the same direction by means of the planet wheels m and e, and
will cause point to retrograde to , and then to ". In this manner a
control is exercised, but the angular extent of the position of no motion
will be relatively large, that is to say, from about to ", and the
precision of the control will be not nearly so great as when the shifting
cccentric is mounted to turn on a special crank axis.
As shown in another arrangement illustrated in Figures 5, 6, and 7,
an eccentric turning on a special axis may be emploved even where the

page_text: pinion m is smaller than e, in which case, as previously explained, the
direction of motion of d will be reversed. In this instance the follow-
ing arrangement is adopted :-Between the wheel & which turns in the
reverse direction to f and eccentric b is placed an intermediate con-
nection consisting, for example, of a frame i working up and down
upon the shoulder j of the shaft, and by which it is guided. On the
wheel d is placed a stud, which moving therewith in the direction of
the arrow 3 carries with it the frame i in an upward direction, for
example Figure 7, and thereby moves also in an upward direction
another stud ¹ fixed on the eccentric b. These two studs are furnished
with sliding blocks working in lateral slots formed on the frame i. It
will be readily seen that the rotary motion imparted in the direction of
arrow 3 will thus be transmitted in the inverse direction 4 to the
eccentric by the agency of the frame i and the studs, ¹, and consc-
quently the rotation of the motor will be also reversed in the direction 4
as also that of g. If now it be supposed, as above, that the attendant
who has moved the machine in the direction 1 stops, and that the
motion of the motor transmitted to g in the direction 4 or 1 continues,
the point will become stationary, as before, but the impulsion of g in
the direction 4 (Figure 5) will reverse the angular motion that the
attendant had imparted to m in the direction of 2, and consequently the
apparatus will be under the required control. The same result might
be obtained by substituting for frame i any other intermediate con-
nection, for instance, by means of a bevel pinion having its axis
normal to the line a, a, and gearing with two wheels mounted
laterally, one on d and the other on b. In this way any other arrange-
ment might be operated.
Figures 8, 9, and 10 illustrate another modification. The importance
has already been mentioned of the optional amplification of the angular
movement placed at the disposition of the attendant to enable the
distributing slide valves or other controlling organ to be shifted with
less power, and the arrangements above described give in this respect
all the latitude of variation that may be desired by the employment of
a differential movement.
I will now describe another arrangement, which within practical
and ordinary limits may also be advantageously employed for obtaining
the same result, that is to say, the amplification of the angular move-
ment of control in the hand of the attendant.

page_text: In Figures 8, 9, and 10, the parts and details designated a, a', a¹¹, b,
c, c, in the preceding Figures are reproduced. a is again the pro-
longation of the driving shaft; j, a plate forged on this shaft and
separating the eccentric from the wheel d by which it is operated;
n, connecting stud, by which the wheel & carries with it the eccentric b.
In front of the plate ; is placed a support or bearing &, connected to j
by bolts 8, 8, 8", or otherwise. This bearing receives shaft 7, by which
the attendant moves and controls the motor by means of wheelf. The
shaft carries a pinion g gearing with a wheel m, which is in one with
the pinion e of the wheel d; m, e, are mounted on and have bolt s¹ for
their axis. It will be readily understood on examining the Figures that
the angular motion of wheel f is by these arrangements considerably
amplified relatively to that of wheel d and to the shifting of 6, and will
be generally more than sufficient. This arrangement therefore con-
stitutes a practical and satisfactory solution of the problem given. As
it may happen that the useful effect produced by this system of gearing
may be relatively high, and that in consequence the total amount of
friction may be insufficient to prevent all backlash or recoil under the
variable resistance of the eccentric b a flat washer is placed on shaft
between the bearing & and the wheel f, and on the same squared part
of the shaft as f, and between this washer and f and clastic washer =',
the bearing is thus pressed by the washer z between the shoulder l
of shaft and the washer z. By means of a nut f¹ the pressure may
be so regulated as to produce the additional friction necessary to ensure
the requisite stability of the apparatus. This completes the arrange-
ment, which it is believed will be of considerable service in many
cases.
Figure 11 shows another arrangement. a, driving shaft; b, shaft
communicating the shifting movement to the eccentric 8 of the dis-
tributing slide valves, or to any other controlling organ used; d, hand
wheel operated by the attendant; e, screw working through the wheel d
at a certain distance from the centre of shaft a, and turning around the
latter by the rotation of wheel d; f, toothed wheel keyed on shaft a;
9, pinion gearing therewith and keyed on screw e; h, skew wheel keyed
on shaft b; and k, skew pinion keyed on screw e and gearing with h.
The ratio of wheels f, g, is the same as that of wheels h, k.
It will be readily seen that by turning wheel d in one or other
direction an angular movement will be imparted to shaft b, which move-

page_text: ment may be as small as may be desired for a large angular movement
of wheel d. The wheel d in turning carries with it the two planet
pinions g, k, and if these two pinions had straight teeth they would of
course merely roll around their respective wheels without producing any
angular movement of the wheel relatively to f, their ratios being
equal, but the pinion g in rolling round the wheel f, which is fixed,
turns the screw e in its nut, which is part of the hand wheel; there is
therefore a longitudinal movement of the screw e, and of the two
pinions and , relatively to the wheel d. The effect of this longi-
tudinal movement is that the pinion / having skew teeth imparts to the
wheel in one direction or the other, according to the direction of the
tangent to the teeth, a small angular movement, which is proportionate
to the inclination of the teeth, and which effects the shifting of the
eccentrics or of the distributing valves, or other controlling organ
employed; this effect being produced by an angular movement of the
wheel d, as great as may be desired, and determined by the proportions
of the wheels, the pitch of the screw e, and the inclination of the teeth
of the skew wheels hand k. This method of amplifying the movement
is another means, which may be serviceable in many cases, and may be
varied in arrangement and detail according to requirements.
Figure 12 shows a modification of the mode already described of
employing gear wheels for amplifying the angular movement for shifting
the eccentric or for operating any other controlling apparatus. In this
modification bevel wheels are employed which have the advantage of
amplifying the angular movement at the disposition of the attendant to
as great an extent as may be desired in practice, so that less effort will
be required to reverse the slide valve or other controlling organ. The
attendant by turning the wheelf which is mounted loose on the end a
of the driving shaft transmits to the eccentric through stud " and
toothed gear g, m, c, d, an angular movement in the same direction, but
slower than that of f. In this manner the eccentric is shifted upon its
eccentric axis a" in the direction required for turning the crank the
same way as the wheel f. If the movement of wheels f and g be
then arrested, shaft a¹, a", which continues to revolve carries with it
spindle c, h, and wheels m, e. The wheel in moving around pinion g
receives rotary motion about its axis, which is transmitted to wheel d by
pinion c. It will thus be seen that wheel d will receive a compound
rotary motion composed of a movement in the same direction, and of the

page_text: same angular amount as that of the crank by the operation of pinion e
acting as a carrier, and another movement in the opposite direction and
of less angular amount transmitted by the same pinion e and due to the
rotation of wheel me on pinion g. The result of the combination of these
two movements is a rotary motion in the same direction as that of the
crank but of less amplitude, so that the eccentric will be soon overtaken
by it, and will consequently return to the position of no motion. The
wheel d is made in two parts, loose on the axis and has a flange around
its periphery to which is bolted a cover / enclosing the gear. The
spindle e, h, turns in a bearing on the motor shaft ; disked clastic
washer regulated by a nut f¹, which together with the flat washer =¹
ensures sufficient friction upon the hub of wheel to prevent all back
lash under the varying resistance of eccentric b.
It may be objected that in the planet motion arrangements of
controlling apparatus described and shown in Figures 1, 2, 3, and 4, the
two forces applied in contrary directions at the points of contact of the
wheel and pinion gear g, m, and d, e, will tend to produce a torsion on
the hand wheel which supports spindle h, and it is possible that under
certain circumstances the great friction between the gears or on their
axis would render such arrangements difficult of employment.
Figures 18 and 19 show a modification of the above described arrange-
ments of controlling gear, by which all torsion and loosening of the
hand wheel is entirely avoided, without however sacrificing the
advantages of simplicity and efficient action possessed by such arrange.
ments. To this end the spindle 4 of the planet pinion is supported at
each end in two bearings carried by a circular casing f' fixed to the
hand wheel, or as in the particular instance illustrated to a pinion f
substituted for the hand wheel. The casing f' completely encloses
the whole of the planet gear which is made as small as possible,
and is secured from torsion or displacement by a bearing upon the
extension a' of the shaft, and another on a circular collar formed on the
movable wheel d. The action of the apparatus is in other respects the
same as in the former arrangements as may be seen by comparing
the Figures. It will be observed that the motion is in this case supposed
to be transmitted to the apparatus from the hand wheel by an endless
chain in gear with a pinion i. On the axis ; of this pinion is keyed a
weel k which gears with the pinion fast with the casing f¹. The
diameter of wheel is large in proportion to that of pinion in order to

page_text: reduce the number of revolutions, which is generally considerable, to be
imparted by the hand of the attendant. This arrangement is especially
useful for apparatus of small dimensions and operated directly, in which
case the hand wheel would be keyed on shaft j.
Another advantage attending the use of this intermediate shaft when
the apparatus is employed in ships of war is that the motion may be
reversed for turning the servo-motor windlass working the rudder in the
same direction as the hand steering wheels, the direction of motion of
Moreover, in order in
the hand wheel remaining the same as usual.
this particular application to rudders, for example, to prevent the tiller
from moving beyond its due limits and striking against the sides of the
ship, it is necessary to limit the number of turns of the hand wheel or
the machine in one direction or the other. For this purpose the axis j
is screw-threaded, and by its rotation causes a nut which is prevented
from turning by the cross bar m² to travel along it. After a certain
number of turns the nut arrives at the end of its course, and presents
itself in the path of one of the lugs p, p', mounted on the wheel & and
pinion respectively, whereupon the motion of the hand wheel is arrested
i
and consequently that of the machine.
Figures 27, 28, and 29 represent another arrangement 'of differential
gearing on the principle of that before described and producing the
same results; Figure 27 is a longitudinal section of the arrangement;
Figure 28, a transverse section on line c, d, Figure 27; and Figure 29, a
similar section on line a, b, Figure 27. It will be readily seen on
examining the Drawing that the rotation of the hand or chain wheel A,
and its eccentric hub will displace the centre of wheel B which has an
internal ring of, say 10 teeth. During this movement each tooth of
wheel B enters successively between the teeth of wheel C keyed on the
shaft, and having, say only eight teeth. The wheel B thus advances
two teeth for one revolution of chain wheel A, and this differential
movement is sufficient to shift the eccentric D (which is connected by a
lug to wheel B) from the "stop" position to the positions of forward or
backward gear F, G, or B, G. On the return movement, that is to say,
when the crank shaft commencing to move destroys the effect of the
shifting movement produced by the attendant, one revolution of the
engine is necessary to return the eccentric to stop.
It will be evident that the number of teeth in each of the two wheels
and the eccentricity of the hub is dependent on the degree of retardation

page_text: desired, and in each case it will be necessary that the teeth should be so
formed as to prevent their jamming. By increasing the diameters the
teeth may also be made longer and more taper, so that two or three teeth
will always be in contact. Where it is desired to control an ordinary
eccentric the internal toothed wheel would be keyed on the shaft, the
other wheel being loose for connection with the eccentric.
Figures 20 and 21 show a simplified arrangement of controlling gear,
in which a spiral sleeve is employed, such as described in a former
Patent granted to me, bearing date June 3rd 1874, No. 1934. f is the
driving shaft with a cranked part 8, on which is mounted the eccentric n
with its two straps i, i. Besides the spiral j formed on the prolongation
off there is also a screw j', on which works a nut and pinion operated
by any one of the means before described. The sleeve m described in
the said former Patent is also used in this case, and is caused to par-
ticipate in the traversing movement of nut 1, to which it is connected
by a flange m", but the long pitched spirals formed on its exterior in
the former case, which by turning the socket n' shifted the eccentric n,
are now formed on the interior of the sleeve m, which thus forms a nut
working on the spirals j, j³, on screw j and intersecting the shorter
pitched screw j. Thus it will be readily seen that any difference of
velocity in the rotation of pinion and driving shaft ƒ will cause the
sleeve m to traverse along the extension of the shaft, and at same time
by working in the spirals, ³, to receive a slight rotary motion, which
is transmitted to the eccentric through rod n', whereby the eccentric
is shifted as desired, the same as by the socket ¹ in the former Patent
referred to.
It will be remarked that in Figures 20 and 21 the pinion is operated
and controlled in a similar manner to that described with reference to
Figures 18 and 19 as regards the limitation and regulation of its motion.
The pinion is made of sufficient breadth to gear constantly during its
traverse with the wheel by which it is operated.
The Invention further relates to improvements in the continuous
rotary servo-motors described in the said Patent before referred to, in
which a variable normal lead and partial expansion are obtained by
means of a shifting eccentric turning upon a crank axis, the true centre
of the eccentric itself moving in the arc of a circle passing through the
centre of rotation of the main or driving shaft.

page_text: Figure 13 shows a general view of this apparatus with the present
improvements, which are applicable not only to this apparatus in its
various applications, but also to other similar apparatus. a, a', steam
cylinders (other liquid or gaseous fluid may be used) inclined towards one
another at an angle of 90°. Their pistons will be designated by b, b₁;
c, c¹, piston rods, and d, d, connecting rods; e, e¹, guides; f, shaft
crank at k; f', counterpoise for moving parts of the machine; 9, 9', valve
chests, the slide valves contained therein being designated by h, h';
i, 2¹, eccentric rods; n, shifting eccentric turning on the cranked
portions of the shaft f. The shifting of the eccentric is effected by either
of the methods described. That shown in Figure 13 is the same as in
the previous Patent, and it is therefore unnecessary to again describe
it, but the method shown in Figures 1 and 2 might be employed equally
well, or that shown in Figures 8, 9, and 10, which is represented as
applied for this arrangement in Figure 12, or that shown in Figures 3
and 4, or that shown in Figures 18 and 19 might be used. The rotation
of shaft is transmitted by pinion and wheel p¹ to the drum », which
carries the windlass to be operated. When the servo-motor windlass is
employed for raising weights or for any analogous purpose the wheel p¹
may without inconvenience be keyed directly on shaft q. But for
certain particular applications, for example for working rudders, it is
necessary to provide against the servo-motor or its connections, being
rendered unserviceable by an accident, when it would be necessary to
work the rudder temporarily by hand.
P
In the machine shown provision is made for such an event by an
arrangement which may be used with advantage in other similar
circumstances. The drum on which is wound the tackle for working
the rudder is caused to turn with shaft 7 by means of a key r³, which
allows the drum to move longitudinally along the shaft. This longi-
tudinal movement is imparted by a hand wheel and screw ¹ working
through a nut and connected to a cross bar z² fixed in the drum », and
passing through a slot in shaft q. At the ends of the drum arc clutches
geared at will with either of two other clutches, of which one is on
wheel and the other on pinion x. This pinion is loose on shaft q, as
likewise wheel p', and it is geared by a pitch chain with the hand
steering wheels by which the rudder is worked in case of accident to the
servo motor. It will thus be seen that the hand can be readily sub-
stituted for the steam steering gear, or vice versa. Suppose the dram to

page_text: be in the position Figure 13, in gear with wheel p', and operated by the
servo-motor; in this case the barrel of the aft steering wheel is locked
and serves as a purchase for the drum for working the tackle.
If it be desired for any reason to steer with the wheel on the bridgo
geared by a chain with pinion x it is only necessary to put drum » in
gear with pinion x by working screw v, the barrel of the aft steering
wheel serving always as a purchase. If on the other hand it is desired to
steer with the wheel aft the drum must be prevented from turning,
so that it may act as a purchase for the aft wheel. For this purpose it
would be geared again with wheel p', and the latter would be locked by
means of a bolt fitted in the frame of the machine, and passing between
the teeth of the wheel. These changes may be effected with the
greatest rapidity, so that the working of the rudder is not appreciably
interrupted.
To prevent the 'coils of the chain wound on drum riding one upon
another the chain is passed over a double pulley o' mounted on a carrier
on a screw shaft o², along which it is caused to traverse simultaneously
with the winding of the chain upon the drum by the rotation of said
shaft, which is geared with and receives motion from the drum » by an
endless chain and chain wheels. By this means the chain is always
guided on to the part of the drum on which it should be wound, and all
riding of the coils on one another is prevented.
In certain cases, as for example that of an engine working at a com-
paratively low speed, it may happen that an extent of angular motion
not exceeding a fraction of a turn may suffice to ensure the requisito
precision of working. Figures 22 and 23 show an arrangement adapted
for this particular case, in which the attendant acting on the circum.
ference of a large hand wheel shifts the eccentric directly through the
medium of pin u³, the extent of motion being from about 150 to 160
degrees.
The arrangement shown in Figures 24, 25, and 26 may also be
employed, preferably on merchant vessels. a, main driving shaft, made
hollow throughout its length; b, shaft working inside of shaft a, by

page_text: thereon from the crank pin c of shaft b; the shaft d has at its other
end a crank arm d" and pin d by which the slide valve rods are worked.
It will be readily understood, as shown in the diagram, Figure 26,
that the attendant by rotating shaft in one or other direction shifts
the position relatively to the main crank of the crank pin d, which i
operates the valve rods and thus controls the operation of the engine.
The crank pin c being fixed at a short radius from the axis of shaft bit
will be seen that the attendant operating this shaft will have at his
disposition an extent of movement equal to 180°. These arrangements
may be varied at will according to circumstances. The hand wheel
may be made sufficiently large to overcome with ease the resistance of
the valves. By means of suitable connections the fly wheel may bo
used for steering by hand.
Figures 15, 16, and 17 relate to the conjugation or controlling by
one attendant of an assemblage of servo-motors having continuous rotary
motion, or of servo-motors having continuous rotary motion, and others
having alternate or other motion. The conjugation in accordance with
the principles enunciated is effected by means of abscisses and of various
ordinates or co-ordinates upon various planes of projection or in space.
It is evident that these co-ordinates might be delineated or defined upon
surfaces of different kinds, plane, cylindrical, conical, or irregular.
These co-ordinates might be convergent or non-convergent, &c., the
principle upon which the conjugation of servo-motors is effected being
always to assemble in one point the centre of general direction the
various respective trajectories or representative paths of the translation
to be effected by each servo-motor in order to construct therewith in
space a total resultant trajectory which defines and completely controls
the ensemble of the movements of the apparatus operated, and which
may not be similar to any one of the partial trajectories respectively
described in accordance with each co-ordinate.
Modifications of this general solution may be combined in any
indefinite number.
For continuous rotation I have given as an example the modification,
Figures 15 and 16. Let it be required to control a servo-motor having
continuous rotary motion, or of other kind, by the hand wheel a, by
means of which the attendant actuates a shaft b and through the latter
transmits motion by any suitable gearing for working the controlling

page_text: gear, and let it be also required to control simultaneously and according
to a different law another servo-motor of any kind. The arrangement
to suit the particular case in question may be as follows:-Hand
wheel a is mounted on a sleeve a capable of sliding in bearing a" and
upon shaft b, the shaft is made square or has a keyway so that a¹ and
b may revolve together and also slide one on the other longitudinally.
The sleeve a¹ is grooved at a to receive a collar, by which in moving
along shaft bit acts upon the end of a bell-crank lever d, d', or other device
controlling the second servo-motor. It will be at once evident that the
attendant both whilst turning or holding the hand wheel stationary may
move it to and fro together with sleeve a', and in this way any point on
the hand wheel, for example on the periphery or handle c or other point
on which the attendant acts, will constitute this centre of general
direction for the translation of the object operated according to two
co-ordinates for controlling two servo-motors, for example, heavy
artillery may in this manner be trained horizontally by means of hand
wheel a, and elevated or depressed by lever d, d'. The training of a
heavy gun mounted on a small gunboat may also be performed by the
above means, a being used for working the rudder either with the aid of
a servo-motor or by screw or other gearing, and d, d¹, for elevating or
depressing the gun through the medium of a steam, hydraulic, or other
servo-motor.
It is evident that if by a suitable arrangement a third co-ordinate be
established by a third and distinct transmission of the rotation of a, and
the longitudinal traverse of a¹, a third law or trajectory distinct from
the two first would be created in accordance with which the point or
centre of general direction will control the apparatus, as in the two
former cases, similarly for an indefinite number of co-ordinates and of
servo-motors, in accordance with the Specification of a former Patent,
granted to the present Inventors, dated September 4th, 1872, No. 2635.
The arrangement illustrated may be placed either horizontally,
vertically, or at any desired angle of shaft b. These means may be
adopted for coupling a servo-motor with a motor not so controlled, or
other mechanism, or for connecting two mechanisms together, whether
; operated by hand or otherwise, as for example, for working small guns
on board of torpedo boats. The same combined movements may also be
used for actuating gearing of any kind, such as of auxiliary servo-
motors.

page_text: Figure 17 shows another example of the method of coupling two
servo-motors having continuous or non-continuous rotary motion, the
same being applicable for training great guns and other purposes; m,
n, horizontal and vertical connecting rods jointed together at x; con-
necting rod m is also jointed to a lever p, and rod n to lever q, the said
levers being mounted in any suitable plane or replaced by other
connections or means of governing the controlling gear of each servo-
motor. It will be at once seen that x is the centre of general direction,
which on being moved horizontally oscillates lever p for training the
gun, while on the other hand by rising a, lever q will be operated
vertically for elevating or depressing the gun. If point be shifted.
more or less obliquely, the two movements may be combined together
under the control of the gunner who lays the gun.
Having described the nature of the Invention and the manner of per-
forming the same, I declare that what I claim as the Invention to be
protected by the herein-before in part recited Letters Patent is,-
1st. Controlling gear having a shifting eccentric, in which the
amplification of the angular motion at the disposal of the attendant is
obtained through tho medium of differential spur, screw, or other gearing,
as illustrated in the several arrangements shown in Figures 1, 2-3, 4—5,
6,7-8, 9, 10-11-12-18, 19-27, 28, and 29, of the Drawings.
2nd. The arrangement of controlling gear with spiral sleeve, described
and illustrated with reference to Figures 20 and 21 of the Drawings.
3rd. In a servo-motor having continuous rotary motion (a), the
arrangement consisting of a drum r capable of longitudinal movement
on shaft
q, by the action of a hand wheel for putting the same in gear
with the small chain pinion or with wheel p', according as it is desired
to steer by hand or steam, substantially as described and shown in
Figures 13 and 14. (b) the employment, as described and shown in
Figure 13 of a double pulley o', having a traversing movement, around
which the chain from the drum is passed in order to prevent the coils
riding one upon the other, and thus avoid breakage of the chain which
might otherwise occur by one coil of the chain slipping off another on to
the drum.
...
mt
11
10

page_text: Figures 24, 25, and 26, respectively; whereby an extent of angular
motion not exceeding a fraction of a turn performed by the attendant
may suffice to ensure the requisite precision of working as specified.
5th. The methods and arrangements shown in Figures 15, 10, and 17,
of conjugating under the hand of a single attendant the controlling
gear of an assemblage of servo-motors, whether such servo-motors all
have continuous rotary motion, or one or more of them have continuous
rotary motion and others have alternate or other motion; the principle
upon which the conjugation of servo-motors is based being always the
assemblage in one point, the centre of general direction of the various
respective trajectories or representative paths of the translation to bo
effected by each servo-motor, in order to construct therewith in space a
total resultant trajectory, which defines and completely controls the
ensemble of the movements of the apparatus operated, and which may
not bo similar to any one of the partial trajectories respectively described
in accordance with each co-ordinate.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Third day of May, in the
year of our Lord One thousand eight hundred and seventy-six.