IMPROVEMENTS IN AND CONNECTED WITH SCREW PROPELLERS
Year: 1877

page_text: LETTERS PATENT to Alexander Carnegie Kirk, and Edmund Hunt, of Glasgow,
in the County of Lanark, North Britain, Engineers, for the Invention of
"IMPROVEMENTS IN AND CONNECTED WITH SCREW PROPELLERS."
Sealed the 2nd November 1877, and dated the 12th May 1877.
PROVISIONAL SPECIFICATION left by the said Alexander Carnegie Kirk and
Edmund Hunt at the Office of the Commissioners of Patents on the 12th May
1877.
ALEXANDER CARNEGIE KIRK, and EDMUND HUNT, of Glasgow, in the County of
Lanark, North Britain, Engineers. " IMPROVEMENTS IN AND CONNECTED WITH
SCREW PROPELLERS."
This Invention relates to the constructing of screw propellers in an improved
manner and with improved mechanisin for feathering the blades thereof.
In carrying out the Invention each blade is formed with a shank, which has two
or more journals or bearing surfaces turned on it, the innermost one being the
smallest, and intermediate ones, if any, intermediate in size. A collar is formed on
the shank just within the outermost journal, and this collar is at one part formed
with a lug, serving as a lever for turning or feathering the blade by. The propeller
boss is formed with sockets to receive the blade shanks, and it is divided in a plane
at right angles to the shaft and passing through the axes of the blade shanks, the
divided parts being bolted together when the blade shanks are in place, and the
collars on the shanks, holding them in the sockets. The axes of the blade shanks
are not directed to the centre, but each to a side of it, which admits of the shanks
being made longer for a given size of boss and of their being better held than if
directed to the centre in the ordinary way. The propeller shaft is made tubular, and
a feathering shaft is passed through it, and is arranged to be turned by worm wheel
gearing provided at a coupling of the propeller shaft inside the vessel. The
feathering shaft extends through to the after part of the boss, and has there fixed on
it a lever piece formed with two or more armis, according to the number of blades.
The arms of the lever piece on the feathering shaft are connected by links, fitted by
preference with ball joints to the lugs or levers on the blade shanks; and through

page_text: these parts the blades are turned in their sockets whenever the feathering shaft is
turned in or relatively to the propeller shaft.
The arrangement is applicable to propellers with two or more blades, and when
there are two blades these can be turned into fore-and-aft positions, and the propeller
can be set with the blades vertical so as to offer the least possible obstruction when
the vessel is proceeding under sail alone, whilst in any case the blades can be set to
any pitch within the limits for which the parts are designed. The feathering
details are covered by a shell forming the after part of the propeller boss.
Instead of connecting the feathering shaft to the blades' shanks by the lever
piece and links, worm wheel teeth may be formed on the shank collars, and worms
gearing therewith may be geared to the feathering shaft by spur wheels or by worm
wheels and a worm on the feathering shaft; or instead of the shanks being held by
annular collars they may be formed with screw threads, the sockets being internally
screwed to correspond so that the shanks may be screwed into their places, and in
feathering be screwed out or in a little. When the shanks are screwed in in this
way the boss does not require to be divided to admit them into their sockets, whilst
arms or levers for turning them by can be inserted and fixed through fore-and-aft
openings made for them in the boss."
When it is wished to have the power of feathering the blades whilst the propeller
is in motion, and when it is preferred not to have the propeller shaft tubular, the
feathering details are modified so as to be adjustable by means of a vertical shaft or
spindle passing down a tube at the after stern post behind the propeller. The
vertical adjusting shaft has at its lower end a worm in gear with a worm wheel on
a horizontal screw spindle, situated in or partly in a stationary cylindrical casing,
which projects into the back of the propeller boss, the boss being by preference
fitted with lignum vitae or other suitable bearings to revolve on the casing. The
screw spindle imparts a forward or backward movement to a suitably guided nut or
internally screwed block, on which a ring or cap is fitted to turn loosely; and this
ring or cap, which rotates with the propeller, is connected by links to the lugs or
levers on the blade shanks, so that the forward or backward movement produced
by the worm wheel and screw gearing will turn the blades in their sockets.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Carnegie Kirk and Edmund Hunt in the Great Seal
Patent Office on the 10th November 1877.
ALEXANDER CARNEGIE KIRK and EDMUND HUNT, of Glasgow, in the County of
Lanark, North Britain, Engineers. "IMPROVEMENTS IN AND CONNECTED WITH
SCREW PROPELLERS."
Our said Invention relates to the constructing of screw propllers in an improved
manner and with improved mechanism for feathering the blades thereof.
Our Invention comprises improved modes of adapting the shanks of the blades to
the boss, and of holding them in the boss; and also improved arrangements or com-
binations of parts for communicating a turning or feathering motion to the shanks
of the blades. Each shank is formed with two or more journals, the innermost one
being the smallest and intermediate ones, if any, intermediate in size.
In some modifications a collar is cast or formed on the shank just within the
outermost journal; and this collar is at one part formed with a lug serving as a
lever for turning the blade by.
In other modifications a screw thread is formed on the shank of each blade, and
a counterpart or internal screw thread is formed for it in the socket in the boss, the
blade shank being screwed a little inwards or outwards when it is feathered. The
sockets formed in the boss to receive the blade shanks are made so that each shank
passes across at the side of the shaft or central part of the boss, which admits of the

page_text: shanks being of greater length and better held than when they are placed with
their axes directed towards the centre.
In some modifications the boss is divided so that one half of each shank socket is
in each part, and the two parts are securely bolted together after the blades are
placed in position.
The feathering or blade turning mechanism is in some modifications made to
operate by a feathering shaft passing through the centre of the propeller shaft and
connected with gear for turning it inside the vessel; arms on the after end of the
feathering shaft are directly connected by links to the lugs or levers on the blade
shanks; or as in some modifications herein-after described toothed gearing transmits
the motion of the feathering shaft to the blade shanks.
In other modifications the lugs or levers on the blade shanks are connected by
links to a ring or disc, to which an endways movement is iniparted by a longi-
tudinal screw held in a non-revolving or stationary casing or piece in an after
compartment of the boss, and having formed or fixed on it a worm wheel, with
which there gears a worm that is movable from the deck or stern of the ship by
means of a shaft passing down a vertical pipe abaft the propeller. With this last-
described arrangement the blades can be turned or feathered whilst the propeller
is in motion, and the propeller shaft does not require to be tubular.
And in order that our said Invention and the manner of performing the same
may be properly understood, we hereunto append four Sheets of explanatory
Drawings, to be herein-after referred to, and representing modifications of our
improved screw propellers. In these Drawings the same reference numerals are
used to mark the same or like parts wherever they are repeated.
Figure 1 on Sheet 1 of the Drawings is an elevation of a modification of our
improved propeller which is being fitted to Her Majesty's ship "Carysfort."
Figure 2 is a vertical section, showing in side elevation the parts for turning the
feathering shaft, and which parts are inside the vessel in this modification.
Figures 3 and 4, on Sheet 2 of the Drawings, are longitudinal sections of the boss
as taken at right angles to each other.
Figure 5 is a plan of the propeller with the blades in a vertical position; and
Figure 6 is an end elevation as with the after shell or casing of the boss removed.
Figures 7, 8, are an enlarged sectional elevation and a horizontal section of parts
shown in Figure 2; this "Carysfort" propeller is fitted with two blades, 1, held in
a boss, 2, 3, 4, which is for the most part of a spherical form externally, and which
is formed with an eye or socket to fit on the tapered end of the propeller shaft 5.
The shank 6 of each blade 1 is formed with two journals, an outer larger one 7. and
an inner smaller.one 8, and with a collar 9 just within the outer journal 7. The
main portion of the boss is divided into two parts 2, 3, by a plane at right angles
to the shaft 5, and is formed with sockets or bearings for the journals 7, 8, of the
blade shanks 6, one half of the bearings being in each part 2, 3, and when these
two parts are bolted together the collars 9 prevent. the withdrawal of the blade
shanks. The axes of the blade shanks 6 are not directed to the centre of the boss
but each a little to the side, as will be best understood from the Drawings, and the
blades 1 are shaped in relation to their shanks 6 and to the boss in such a manner
that when they are feathered or set in a fore-and-aft position, or as nearly so as
is possible, and the propeller is turned so as to make the blades vertical, no parts
of the blades project laterally from the vertical plane of the stern post to an incon-
venient extent.
In Figure 5 the upper blade is shown in full lines in its extreme propelling
position, whilst dotted lines show its position when feathered. The shank collars
are formed with lugs or enlargements, serving as levers for turning the shanks by;
and in these lugs balls 10 are fixed, the balls being connected by links 11, fitted
with spherical bearings to similar balls 12, fixed to a cross head or two-armed end
piece 13, which is fixed on the end of the feathering shaft 14. This feathering
shaft 14 passes through a stuffing box at the back end of the propeller shaft 5, and
extends through the centre of that shaft, which is tubular, to the first coupling 15

page_text: inside the vessel; a shell or casing 4 covers the feathering details, and completes
the after part of the propeller boss.
On the forward end of the feathering shaft 14 there is fixed a sector 16, formed
with worm wheel teeth, with which there gears a worm 17 on a spindle 18, carried
in a bearing fixed to the coupling, and formed with a squared end to receive a
ratchet spanner 19, by means of which the necessary movement is imparted to the
fenthering shaft 14 when required for adjusting the propeller blades in a feathered,
or propelling position. The forward end of the feathering shaft 14 works in a brass
bush fixed in the end of the bore of the propeller shaft 5, and packing material,
which can be tightened by means of segmental plates 20, adjustable by external
screws, is applied between the end of the bush and an inner flange formed on the
sector 16.
Figures 11 and 12, on Sheet 3 of the Drawings, represent a modification adapted
for three blades, Figure 11 being a longitudinal section, and Figure 12 an elevation
with the back cover or casing removed. In this modification the blades 1 are held
in their sockets in the boss by means of screw threads, indicated by dotted lines in
Figure 12, and formed on the inner ends of their shanks 6, and the boss is not
divided to receive the shanks; levers 21, for turning the blades by, are fixed in
the shanks 6 after these are entered into their sockets, the levers being fixed by
screw nuts applied through openings 22 formed in the boss for the purpose. The
links 11, connecting the shank levers 21 to the (three-armed end piece 13 fixed on
the feathering shaft 14, is of a kind shown enlarged in Figures 9 and 10 on Sheet 2
of the Drawings. This link consists of a flattened hoop fitted with a pair of brasses
for each ball 10, 12, which brasses can all be tightened by a single transverse wedge
or key.
Figures 13 and 14, on Sheet 3 of the accompanying Drawings, are longitudinal
sections as at right angles to each other of a modification, in which worm and worm
wheel gearing is employed to transmit the adjusting movement from the feathering
shaft 14 to the blades 1, and Figure 15 is a sectional end elevation.
n
In this modification the blade shanks 6 are formed and held like those of the
first modification, excepting that the collars 9 are formed with worm wheel teeth
in gear with which there are worms 23 on spindles 24, having on them worm
wheels 25 in gear with a worm 26, fixed on the end of the feathering shaft 14.
In this modification a complete worm wheel will require to be fixed on the forward
end of the feathering shaft 14 instead of the sector 16 (Figures 7, 8). Instead of
the intermediate worm spindles 24 being geared to the feathering shaft 14 by
worm wheels and a worm, they may be placed longitudinally, and be geared to the
feathering shaft by spur wheels.
Figures 16 and 17 are longitudinal and transverse sections of a modification in
which a worm 26 on the feathering shaft 14 gears directly with worm-toothed
sectors 27, which are fixed on the blade shanks 6 by screw pins, after the shanks
are entered into their sockets in the boss.
Figure 18 on Sheet 4 of the Drawings is a sectional side elevation of a modifi-
cation of our improved screw propeller, to be used when it is wished to have the
power of feathering the blades whilst the propeller is in motion, and when it is
preferred not to have the propeller shaft 5 tubular.
Figures 19 and 20 are longitudinal sections, as at right angles to each other; and
Figure 21 is a sectional end elevation, each half of it being as taken at a different
part..
The feathering details are modified so as to be adjustable by means of a vertical
shaft 28 passing down a tube 29 near the after stern post behind the
The vertical adjusting shaft 28 has at its lower end a worm in gear with a worm
propeller.
wheel 30 on the outer or back end of a screw spindle 31, situated in or partly in a
stationary cylindrical casing 32, which projects into the back casing 4 of the pro-
peller boss.
The casing 32 is prevented from turning by being fixed to the tube 29 of the vertical
shaft 28, and by the upper end of that tube 29 being passed up through a trunk 33 and
5

page_text: ring 34 in the overhanging part of the ship's stern. The back shell or casing 4 of
the propeller boss is made in two halves, and with internal bearing surfaces 35,
lined with lignum vitæ or other suitable material to embrace the stationary
casing 32 between deep flanges formed on that casing, and lined with lignum vitæ
or other suitable material. The screw spindle 31 works in an internally screwed
prism or piece 36, guided, but so as not to turn, in a socket in the stationary casing
32, and formed in the same piece with a deeply flanged pulley 37, which pulley is
moved inwards or outwards by the turning of the screw spindle 31 in one direction
or the other. Between the flanges of the pulley 37 there is placed a ring 38, which
can revolve freely on the pulley, being fitted with lignum vitæ or other suitable
bearing surfaces, and consisting of two halves which are bolted together when placed
in position. This ring 38 is formed with diametrically opposite projecting pins 39,
which are connected by links 40 to pins 41 fixed in the lugs of the collars 9, formed
(as in the first modification herein-before described) on the shanks 6 of the propeller
blades 1; and these blades are feathered or turned by the action of the links 40
and the inward or outward movement of the pulley 37. The ring 38 on the
pulley is made to turn with the propeller in consequence of the pins 39 being
in contact with guides 42, formed in the boss casing 4. The pulley piece 37 is
additionally guided by a spindle 43, projecting from the centre of its inner side,
and working in a guide socket formed for it in the end of the propeller shaft 5.
The vertical adjusting or feathering shaft 28 has a screw thread formed on it
near its upper end to work a nut 44, which is put on it, in accordance with the
movements transmitted to the propeller blades, and so as to indicate the position of
the blades. The nut 44 is formed with a tongue which projects through a slot in
an inner tube 45, and into a guide groove in the outer tube 29. The slot is helical
and the guide groove straight (or vice versa), so that as the nut 44 is moved up or
down it turns the inner tube 45 (at a greatly diminished rate, as compared with
that of the shaft 28). The inner tube 45 has a disc or dial 46 formed or fixed on
its upper end, and thereby shows the position or pitch of the propeller blades at all
times.
Some of our herein-before described improvements are applicable to screw pro-
pellers having blades, the shanks of which are directed towards the centre of the
boss instead of being deviated therefrom; and some of the improvements are
applicable to screw propellers, the blades of which are fixed in position by bolts or
keys, after being adjusted.
Having thus particularly described our said Invention, and the manner of per-
forming the same, we have to state that we do not restrict ourselves to the precise
details herein described or delineated; but that what we believe to be novel and
original, and claim as the Invention secured to us by the herein-before in part
recited Letters Patent is:-
1. The combination of parts forming a feathering screw propeller, herein-before
described with reference to Figures 1 and 3 to 6 of the accompanying Drawings.
2. The combination of parts forming a feathering screw propeller, herein-before
described with reference to Figures 11 and 12 of the accompanying Drawings.
3. The combinations of parts forming feathering screw propellers, herein-before
described with reference to Figures 13, 14, and 15, of the accompanying Drawings.
4. The combination of parts forming a feathering screw propeller, herein-before
described with reference to Figures 16 and 17 of the accompanying Drawings.
5. The combination of parts forming a feathering screw propeller, herein-before
described with reference to Figures 18 to 21 of the accompanying Drawings.
6. The securing of the blade shanks by means of collars (9) formed on them, and
by placing them between two parts of the boss which are bolted together, substan-
tially as herein-before described.
7. The securing of the blade shanks by screwing them into the boss, substantially
as herein-before described.
8. The transmitting of turning or feathering movements to the blade shanks by a
central feathering shaft extending through a length or lengths of the propeller shaft

page_text: and turning a cross head or armed end piece connected by links to levers on the
blade shanks, substantially as herein-before described.
9. The transmitting of turning or feathering movements to the blade shanks by
means of a vertical shaft, which by turning a screw in a stationary piece on which
the back or outer part of the propeller boss revolves imparts an endway motion to
a pulley piece having loosely on it a ring connected by links to levers on the blade
shanks, substantially as herein-before described.
In witness whereof, we, the said Alexander Carnegie Kirk and Edmund Hunt,
have hereunto set our hands and seals, this Ninth day of November, in
the year of our Lord One thousand eight hundred and seventy-seven.