IMPROVEMENTS IN THE CONSTRUCTION OF AND IN THE METHOD OF DRIVING SCREW PRO- PELLORS
Year: 1879

page_text: LETTERS PATENT to John Fisher, of 40, Southampton Buildings, Chancery
Lane, in the 'County of Middlesex, for the Invention of IMPROVEMENTS IN
THE CONSTRUCTION OF AND IN THE METHOD OF DRIVING SCREW PRO-
PELLORS."
Sealed the 21st November 1879, and dated the 23rd May 1879.
PROVISIONAL SPECIFICATION left by the said John Fisher at the Office of
the Commissioners of Patents on the 23rd May 1879.
JOHN FISHER, of 40, Southampton Buildings, Chancery Lane, in the County of
Middlesex. "IMPROVEMENTS IN THE CONSTRUCTION OF AND IN THE METHOD OF
DRIVING SCREW PROPELLORS."
My Invention has for its object improved methods of constructing and driving
the screw propellors of steam ships or other vessels, by which improvements such
screw propellors work more smoothly and with less vibration than is ordinarily the
case, and when set in motion, or stopped, or affected by the movements of the vessel,
there is less shock and less liability of injury to the screw propellor or to the
machinery by which it is driven.
I take a screw propellor of any of the well known kinds, having two or more
blades, and I fit and fix it upon a shaft in the usual way, such shaft being actuated
by steam or other power in the vessel in the ordinary way.
The opening in which the screw revolves is of such length as to allow the screw,
together with the shaft upon which it is fixed, to move backward and forward for
a sufficient distance in the direction of the length of the vessel, the shaft moving
through the stuffing box and other bearings in which it revolves. Within the
vessel I connect this shaft to the main propelling shaft driven by the engine by a
coupling constructed in such a manner that whilst the screw and its shaft are made
continually to revolve when the engine shaft is in motion, they are not prevented
from moving endways at the same time through a certain distance in the way
described. For this purpose I fit the inner end of the screw shaft within the corre-
sponding hollow end of the driving shaft, so that it can slide backward and forward
in the latter, but I arrange one or more longitudinal keys fitted into recesses upon
the shafts, so that it is impossible for one to revolve without the other also revolving

page_text: Or I fit one or more transverse keys or cotters, passing through corresponding slots
in the two shafts, the slot in one or the other of which is of sufficient length to
allow the key to move for a sufficient distance backward and forward in it. I prefer
to make the parts of the shafts where they are thus coupled together of greater
diameter in order to compensate for the diminution of strength caused by the keys
or cotters.
Upon the outer end of the hollow socket described upon the driving shaft I
make or fix a flange of sufficient diameter and strength, and upon the screw shaft
which fits within it I make or fix a corresponding flange at a considerable distance
from the former. Upon the screw shaft between the two flanges I arrange one or
more elastic springs of sufficient strength, and compressed between the flanges
sufficiently to afford the resistance necessary for the purpose hereinafter described.
These springs may be of any suitable description. Helical springs of steel or
other sufficiently strong and elastic material may be used; or a series of concave
elastic steel plates, or in some cases washers or discs of india rubber. Compressed
air or other elastic fluid in cylinders may also sometimes be used as springs.
The action of the apparatus arranged as described is as follows:-When the
engine driving shaft is set in motion for the purpose of propelling the vessel forward
the screw is at the same time made to revolve. A part of the power which is
ordinarily expended in striking and moving the water with the blades of the screw
before the inertia of the vessel has been overcome is in my improved arrangement
expended in compressing the springs described, in doing which the screw with its
shaft moves forward for a short distance, the latter sliding within the hollow end
of the driving shaft. When the vessel is in motion forward the propelling power
of the screw is always exerted against the vessel through the thrust blocks or
bearings upon the driving shaft, which is itself impelled forward by the screw shaft,
with the intervention of the elastic springs described, and the vibration, shocks, and
irregular movements caused by the direct connection of the screw with the driving
shaft are in this way prevented. In the same way the shocks or blows and irregular
movements caused by the action of the waves upon the vessel and upon the screw,
especially in rough weather, are also lessened or prevented; for, if whilst the screw
is propelling the vessel uniformly forward, any sudden cause retards the revolution
of the screw, or hastens the relative movement forward of the vessel, the screw
with its shaft moves somewhat backward in its position, the springs becoming
simultaneously more extended and their pressure reduced, and thus equalizing the
action of the engine upon the screw, and lessening the chance of injury to the
machinery.
Greater smoothness and regularity of movement of the vessel and of the propelling
machinery are thus attained.
My improved apparatus may be modified in various ways to suit varying circum-
stances. The pressure of the springs described may be made adjustable by means
of a moveable disc or ring upon the screw shaft, which disc may be forced forward
to the extent desired by means of screws and nuts for the purpose of compressing
the springs more or less.
"
Or the discs between which the springs are compressed may be made of sufficiently
large diameter to receive between them any desired number of springs or sets of
springs, arranged at equal distances from the shaft (round which springs may also
be fitted). These springs may be coiled around a corresponding number of cylin-
drical bars or pins, firmly fixed at one of their ends into one of the discs, whilst
their other ends pass freely through corresponding holes in the other opposite disc.
In this arrangement the bars or pins described may be also used for the purpose of
transmitting the rotary motion from the driving shaft to the screw shaft, or sliding
keys or coupling boxes may be used for the same purpose.
The bars or pins described may be prolonged through the disc, and may be fitted
with springs or sets of springs round or upon their outer ends also, such springs
being compressed and retained in their positions by collars or nuts upon the outer
ends of the bars or pins. By this method of arrangement, if the movement of the

page_text: screw be reversed for the purpose of propelling the vessel astern, the screw when
first so set in motion moves with its shaft for a short space backward through the
water, relaxing the pressure of the springs first described, and compressing those
last described, through which the reverse propelling action is transmitted to the
vessel.
In another form of arrangement of my improved apparatus the screw propellor is
not fixed upon its shaft, but is itself fitted upon the shaft in such manner that
whilst it is compelled to revolve when the latter revolves it is at the same timo
capable of moving endways upon it to a certain extent. For this purpose the
screw itself may be fitted upon one or more longitudinal keys of sufficient strength
upon the shaft; or it may be attached to the latter by means of one or more trans-
verse keys or cotters in a way similar to that already herein before described.
Springs of sufficient strength are arranged upon the shaft in front of the screw, the
front ends or sides of the springs pressing or abutting against a collar fixed upon
the shaft, or against the sternpost of the vessel, or against other abutment fixed in
the proper position for the purpose.
Springs of a similar kind may also be arranged if desired behind the screw for
the purpose of transmitting the thrust of the screw when going astern to the vessel,
such springs abutting against a collar upon the shaft behind the screw, or against
the rudder post or other sufficiently strong abutment fixed in the proper position
for the purpose.
By my improved methods of constructing and driving screw propellors the springs
described always form an elastic connection between the screw and the vessel, and
they absorb to a great extent and reduce the vibration and blows caused ordinarily
by such connection being inelastic, and in this way the motion of the vessel becomes
more easy and smooth, and the propelling machinery experiences less injury from
vibration, is more durable, and requires less repair than is ordinarily the case, whilst
power is economized.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Fisher in the Great Seal Patent Office on the 22nd November
1879.
JOHN FISHER, of 40, Southampton Buildings, Chancery Lane, in the County of
Middlesex. "IMPROVEMENTS IN THE CONSTRUCTION OF AND IN THE METHOD OF
DRIVING SCREW PROPELLORS."
My Invention has for its object improved methods of constructing and driving
the screw propellors of steam ships or other vessels, by which improvements such
screw propellors work more smoothly and with less vibration than is the case in
such ships or vessels as ordinarily constructed, and when set in motion, or stopped,
or affected by the movements of the vessel in the water, there is less shock and
less liability of injury to the screw propellor or to the machinery by which it is
driven.
For the purpose of my Invention I form an elastic connection between the screw
and the vessel which it propels, and I arrange the screw itself in relation to such
elastic connection so that the vibration and blows caused ordinarily by the connec-
tion being inelastic are to a great extent absorbed and reduced, and in this way
the motion of the vessel is rendered more easy and smooth, and more comfortable
to passengers, and the propelling machinery experiences less injury from vibration,
is more durable, and requires less repair than is ordinarily the case, whilst the
power required for driving the screw is economized, the screw when arranged and
driven according to my Invention, in the manner hereinafter described and shewn,
having the opportunity of selecting its own course within certain limits, and varying
its path to some extent from the fixed and unalterable one which it must follow if
the connection with the engine be rigid.
Where passengers are conveyed in vessels constructed according to my Invention
their comfort and convenience are very greatly enhanced, the movement of the
vessel being smooth and easy, and free from the continuous vibration and jarring
and the necessary discomfort ensuing therefrom, which are invariably and notoriously
experienced in screw steamers in which the connection between the engine and the
screw propellor is rigid and inelastic, and where consequently every inequality of
the action of the screw upon the water, or of the waves upon the screw, is trans-
mitted without mitigation to the structure of the vessel and to its contents. For
the same reason the strength and durability of vessels constructed according to my
Invention are largely increased, the constant disintegration and loosening of parts
caused by the inflexible manner in which all shocks or blows upon the propellor
are transmitted to the vessel being to a large extent reduced, if not entirely pre-
vented, with the resulting benefit of prolonged durability of the vessel and greatly
diminished loss, both inthe cost and frequency of repairs, and in the time occupied
whilst such repairs are in progress.
In thus rendering the connection between the screw propellor and the engine
which drives it clastic and somewhat yielding, instead of rigid and inelastic, I have
imitated the operation of nature under somewhat analogous circumstances; for
instance, in the action of the fins and tail of a fish, or the wings and tail of a bird,
in both which cases the natural mechanism by which motion is communicated to
the propelling apparatus is elastic and yielding, or pliable instead of being absolutely
rigid, and as a consequence it is more effective, more durable, less liable to accidental
injury, and better capable of answering its desired end than if it were without the
elasticity which it always possesses.
In order to put my Invention in operation I take a screw propeller of any of the
ordinary well known kinds having two or more blades, and I fit and fix it
upon a driving shaft in the usual way, such shaft being actuated by steam or other
power within the vessel in the ordinary way. The opening in which the screw
revolves when at work is made of such length as to allow it, together with the
driving shaft upon which it is fixed, to move for a sufficient distance backward and

page_text: forward, or fore and aft, in the direction of the length of the vessel, the shaft
moving longitudinally through the tube and stuffing box and other bearings in
which it revolves.
At a convenient point inside the vessel I connect this screw shaft to the main
propelling shaft driven by the engine by means of a suitable coupling constructed
in such a manner that whilst the screw and its shaft are made continually to
revolve by the engine shaft when the latter is in motion they are not prevented
from moving at the same time endways or in the direction of their length through
a certain distance in the way described. For the purpose of providing for such end
movement without interfering with the communication of the movement of rotation
from the engine shaft to the screw shaft I fit the inner end of the latter within the
corresponding end (which is made hollow) of the driving shaft, so that it can move
or slide backward and forward in the driving shaft; but I arrange one or more
longitudinal keys of sufficient strength fitted into recesses upon both shafts, so that
it is impossible for one shaft to revolve without the other." Or I fit one or more
transverse keys or cotters passing through corresponding slots in the two shafts,
the slot in one or other of the shafts being of sufficient length to allow the key to
move for a sufficient distance backward and forward in it. The parts of the shafts
where they are thus coupled together may be made of greater diameter than would
otherwise be necessary, in order to compensate for the diminution of strength
caused by the openings for the keys or cotters described.
In the accompanying Drawings, which are in illustration of my Invention, the
arrangements described are shewn on Sheet 1, Figures 1 and 4, and on a smaller
scale in Figure 5. a is the engine or driving shaft made of larger diameter and
hollow at its outer end b, into which fits the inner end of the screw shaft c. A slot
is shewn through both shafts at d, a transverse key or cotter being fitted into the
outer shaft b, and the slot in the inner shaft c being made of sufficient length to
allow the shaft c to move backward and forward for a short distance, as shewn in
dotted lines.
In Figure 4, which is a transverse section of the two shafts, two longitu-
dinal keys e, el, are shewn, as well as the transverse slots through the shafts. In
Figures 6 and 8 a modification of the arrangement shewn upon a larger scale,
Figure 6 being a longitudinal section, and Figure 8 a transverse section. a is the
driving shaft, the end of which fits into the hollow coupling c, which is formed or
fixed upon the end of the screw shaft b. Longitudinal keys e, e, e, are shewn
fitted into the shaft a and sliding in corresponding grooves or recesses in the
coupling c, so that the shafts are compelled to revolve together, but at the same
time the shaft b with the coupling c can move longitudinally backward and forward
upon the keys.
Another novel method which I sometimes adopt instead of keys for the same
purpose, especially where the power to be transmitted through the shafts is great,
is illustrated on Sheet 2 in Figures 10, 11, and 13, Figure 10 being a longitudinal
section, and Figure 11 a transverse section. a is the driving shaft; and b, the
shaft which actuates the screw propellor, the shaft being capable of moving for a
certain distance in the direction of its length whilst revolving. The shaft a is pro-
vided with a strong disc or flange c, and the shaft b with a corresponding disc or
flange d. The flange c has strong driving plates e, e', projecting from the surface
and acting against corresponding plates ff, projecting from the flange d.
Between the respective flanges are adjusted friction rollers g, g¹, through which
the power is transmitted from the plates e, e¹, to the plates f, f¹, but which allow
the plates f, f', to move with little friction backward and forward for a sufficient
distance in the direction of the length of the shafts. I prefer to arrange plates of
hard wood, leather, or other somewhat elastic or yielding material between the
friction rollers g, gl, and the plates e, e¹, or f, f', or both, as shewn at i, i, in
Figures 11 and 13, these plates being covered with steel or iron plates h, h³, to
take the pressure of the rollers. Corresponding sets of plates and rollers, as shewn
in dotted lines in Figure 11, may be arranged between those already described and

page_text: shewn, to come into operation in the opposite direction when the movement of the
screw propeller is reversed.
In order to provide an elastic connection between the engine shaft and the screw
shaft arranged so that their relative positions is capable of being altered longi-
tudinally as above described and shewn, I make or fix upon the outer end of the
hollow socket upon the driving shaft, as shewn at b in Figures 1, 3, and 5, a flange f
of sufficient diameter and strength; and upon the screw shaft c which fits within
it I make or fix a corresponding flange g at a considerable distance from f; and
upon the screw shaft c between the two flanges I arrange one or more elastic
springs h of sufficient strength, which can be compressed by means of the loose
collar or flange and the screws kc, k, sufficiently to afford the resistance necessary
for the purpose hereinafter described.
These springs may be of any suitable kind and material; helical springs of steel
or other sufficiently strong and elastic material may be used, as shown in the
Figures, or a series of thin concave clastic steel plates; or in some cases, especially
for small vessels, washers or discs of india rubber may be used, as shewn at h, h, h,
h, h,, on Sheet 2 in Figure 12. Or air or other elastic fluid compressed in
cylinders may be used as springs.
The action of the apparatus, arranged as described and shewn, is as follows:-
When the engine driving shaft a is set in motion for the purpose of propelling the
vessel forward the screw shaft b and screw are at the same time made to revolve.
A part of the power which in ordinary methods of construction is expended in
striking and moving the water by the blades of the screw before the inertia of the
vessel has been overcome is in my improved method of arrangement expended in
compressing the spring h, in doing which the screw with its shaft b moves forward
for a short distance, which it is permitted to do by the arrangement of the keys
and cotters described and shewn in Figures 1, 4, 5, 6, and 8, or by the arrangement.
of friction rollers and plates shewn in Figures 10, 11, and 13.
When the vessel is in motion forward the propelling power of the screw is always
exerted against the vessel through the thrust blocks or bearings upon the driving
shaft a (as shewn on a smaller scale at e, e¹, in Figure 9), which is itself impelled
forward by the screw shaft b through the intervention of the elastic springs h, h,
and the vibration, shocks, and irregular movements caused by the direct and
inelastic connection of the screw to the driving shaft are in this way prevented.
In the same way the shocks or blows and irregular movements caused by the action
of the waves upon the vessel and upon the screw, especially in rough weather, are
also lessened or prevented, for if, whilst the screw is propelling the vessel uniformly
forward, any sudden cause retards the revolution of the screw or hastens the relative
forward movement of the vessel, the screw with its shaft moves somewhat back in
its position, the springs becoming simultaneously more extended or relaxed and
their pressure reduced, and the action of the engine upon the screw is thus equalized
and the chance of injury to the propelling machinery is lessened, whilst the pressure
between the thrust block and the propelling shaft is regulated and rendered more
uniform and constant, and great smoothness and regularity of movement of the
vessel and of the propelling machinery are thus attained.
My improved apparatus may be modified in various ways to suit various circum-
stances and conditions.
The discs or flanges between which the springs are compressed may be made of
sufficiently large diameter and strength to receive between them any desired
number of springs or sets of springs. And other springs or sets of springs may
also be used in the different arrangements described acting in the opposite direction
for the purpose of interposing an elastic connection between the driving shaft and
the screw shaft when the vessel is being propelled astern instead of ahead. This
arrangement is shewn in Figures 5 and 9.
In Figure 5 a second metal spring for this purpose is shewn at h' compressed
between the flange fixed or formed upon the screw shaft b and the loose ccollar or
flange m, which can be tightened against the spring h' by two or more adjustable

page_text: bolts n, n¹. When the screw shaft so arranged is first set in motion for the purpose
of propelling the vessel astern the screw with its shaft moves for a short space
backward through the water, relaxing the pressure of the spring h and compressing
the last described spring h², through the intervention of which the reverse propelling
action is transmitted to the vessel.
In Figure 12 the pressure of the springs is shewn regulated by nuts upon the
shafts.
Figure 7 shows a side view and Figure 8 in transverse section a series of sets of
springs h, h, h, arranged around the shaft a and b.
These springs are shewn arranged round bars, pins, or bolts p, p, p, fixed at one
end into the flange o attached to the shaft a, and compressed between the said
flange and the flange which is attached to the shaft b, and through which the
bolts or bars p, p, p, pass freely.
The bars or bolts p, p, p, are shown prolonged beyond the flange and passing
through a third loose flange s, between which and the flanger a second series of
sets of springs h¹ are also arranged round the bolts, and can be compressed by
means of screwed nuts upon the outer ends of the bolts, as shewn.
When the vessel is being propelled ahead the springs h, h, h, are compressed
between the flanges o and r, the springs h¹ being relaxed, whilst when the vessel is
going astern the springs h' being relaxed; whilst, when the vessel is going astern,
the springs h are compressed between the flanges 7 and 8, the springs h, h, h, being
relaxed.
The bolts or pins p, p, p, may also be used for the purpose of transmitting the
rotary motion from the driving shaft a to the screw shaft b, in which case I some-
times line the holes through which they pass in the flange with bushes of leather
or other somewhat yielding and elastic material; or sliding keys and couplings
may be used to transmit the motion, as shewn in Figures 6 and 8. In Figure 7
the springs are shewn upon only one of the bolts p, those upon the others being
removed in order that the latter may be more clearly seen. On Sheet 4, Figure 15,
all the springs are shewn in place.
Another arrangement which I sometimes use for the same purpose as those
already described, and which may be used either alone or in combination with
them, is shewn on Sheet 3 in Figure 14, in which a spring a is shewn arranged in
front of the screw 6 behind the stern post, the screw shaft c passing through it in
such manner that when the vessel is being propelled forward the spring is com-
pressed to any required extent. A similar spring d is also shown arranged behind
the screw so as to come into operation when the vessel is being propelled astern,
and the spring a first described is consequently relaxed.
In another form of arrangement of my improved apparatus, not shewn in the
Drawings, I do not fix the screw propellor rigidly upon its shaft, but I fit it upon
the shaft (which is not itself capable of moving in the direction of its length whilst
revolving) in such manner that whilst it is compelled to revolve with the shaft it is
at the same time capable of moving backward and forward endways upon the latter
to a certain extent. For this purpose the screw itself may be fitted upon one or
more longitudinal keys of sufficient strength upon the shaft, or it may be attached
to the latter by means of one or more transverse keys or cotters in a way similar
to that already herein before first described. One or more springs of sufficient
strength are arranged upon the shaft in front of the screw, the front ends or sides
of the springs pressing or abutting against a collar fixed upon the shaft or against
the stern post of the vessel or other abutment arranged and fixed in the proper
position for the purpose.
Springs of a similar kind may also be arranged behind the screw for the purpose
of transmitting the thrust of the screw to the vessel when going astern, and also
serving to take up and absorb more or less the blow of the screw when it recoils
from the front springs if raised wholly or partly out of the water by the movement
of the vessel or the waves. The springs described are arranged to abut against a

page_text: collar, upon the shaft behind the screw, or against the rudder post or other
sufficiently strong abutment fixed in the proper position for the purpose.
By my improved methods of constructing and driving screw propellors, as herein-
before described, the springs always form an elastic connection between the screw
and the vessel, and they counteract and neutralize to a great extent the vibration,
shocks, and irregularity of motion caused by such connection being rigid and
inelastic, as in vessels as ordinarily constructed.
Automatic indicators may be arranged showing the amount of compression of
the springs, and consequently the force with which the vessel is being propelled at
any given moment; and such indicators may record their movement automatically
upon paper or other cylinders made to revolve continuously by clockwork in the
method well understood and practised, so that such record may be preserved and
referred to to ascertain the exact power exerted by the screw upon the vessel at
any time.
6. Having now described my Invention, and the manner in which it is to be
performed, I do not confine myself to the precise forms of apparatus shewn in the
Drawings, but I claim :-The methods of allowing the screw shafts or screws of
vessels to move backward and forward in relation to the driving or engine shaft
without affecting the connections by which the former are made to revolve, substan-
tially as described and shewn in the Drawings. Also, the methods of arranging
elastic springs between the screw shafts or screws and the engine or driving shafts
of such vessels, substantially as and for the purposes described and shewn in the
Drawings.
In witness whereof, I, the said John Fisher, have hereunto set my hand and
thin Olt dan of Naumhan in the van of nun I and 1070
Witness,
E. EDWARDS,
40, Southampton Buildings.
JOHN FISHER. (L.S.)

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