IMPROVE- MENTS IN APPLYING AND FITTING SCREW PROPELLERS, AND IN FORMING AND FITTING THE STERN PARTS OF SHIPS FOR RECEIVING SCREWS
Year: 1861

page_text: LETTERS PATENT to Alexander Crichton, of Cork, Superintending Engi-
neer of the Cork Steam Ship Company, for the Invention of "IMPROVE-
MENTS IN APPLYING AND FITTING SCREW PROPELLERS, AND IN FORMING AND
FITTING THE STERN PARTS OF SHIPS FOR RECEIVING SCREWS."
Sealed the 30th July 1861, and dated the 1st February 1861.
PROVISIONAL SPECIFICATION left by the said Alexander Crichton at the
Office of the Commissioners of Patents, with his Petition, on the 1st
February 1861.
I, ALEXANDER CRICHTON, of Cork, Superintending Engineer of the Cork
Steam Ship Company, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN APPLYING AND FITTING SCREW PROPELLERS, AND IN FORMING
AND FITTING THE STERN PARTS OF SHIPS FOR RECEIVING SCREWS," to be as
follows:-
This Invention relates to a novel mode of removing the screw from between
the outer and inner sternposts of a screw steamer, and in the arrangement of
parts for effecting that object, as also to the means or method of closing the
opening between the two sternposts when the screw propeller is removed there-
from, so as to enable the ship to be more readily and accurately steered, and
to prevent the retardation of the ship through the water common to vessels
when under sail and having the screw opening unclosed.

page_text: Instead of providing a trunk or well-hole extending from the head of the
screw space to the upper deck line of a size necessary to admit of the passage
of the screw and frame, and also a bango frame with its fittings, as ordinarily
employed in the navy for lifting vertically the screw propeller on to the poop
or deck in vessels having an inner and outer sternposts; and also, instead of
the ordinary modes or methods of removing overhung propellers, or propellers
which project beyond the rudder; and instead also of any of the arrangements
for feathering the blades of screws, or otherwise moving or removing them or
changing their position for the purpose of enabling a ship to be sailed without
the obstruction offered to her passage through the water by the screw remain-
ing immersed therein, I construct the last length of screw shaft and the parts
and fittings in connection therewith in the following manner :-I connect the
last (or outer) length of shaft with a joint or coupling in the manner of a
hinge, so that when the knuckles or faces of the-joints-stand vertically, the
shaft having the screw upon it, may be raised from the horizontal to a vertical
position. The water-tight gland or stuffing box upon the screw shaft is in
advance of or forward of the joint or coupling, as is also the thrust block.
Suitable bearings are provided for the moveable length of screw shaft to rest
in when at work, and top brasses or bearings may be provided and be placed
in position when the shaft is lowered, and capable of being moved or with-
drawn horizontally or vertically when the screw and its shaft have to be raised or
withdrawn. The last length or piece of propeller shaft need only be of a length
sufficient to enable the point of the lower blade of the screw to come within the
line of the inner sternpost when the screw shaft is vertical and the screw hori-
zontal, but the screw shaft may be turned up to an extent less or more than
90 degrees from its original plane of rotation for the purpose of accommodating
any feature in the internal arrangement of the stern of the ship. For the
purpose of enabling the screw shaft to be raised as described, as also for the
purpose of allowing the screw propeller to be raised and moved inward by
describing a quadrant or any lesser or greater portion of a circle, I divide the
inner sternpost from the boss upwards into two parts or thicknesses leaving
the requisite space between them, and I form a box or hollow
space imme-
diately above the narrower part of such opening for the purpose of receiving
the screw.
Where it is desirable to provide for the removal or renewal of the
screw propeller or its adjustment, examination, or repair, it is only necessary to
continue this water-tight or boxed space up to any convenient height above
the deep load water line to enable ready access to be afforded to the screw;
power may be applied to the screw shaft, for the purpose of raising or moving
it in manner described, either by means of rack and pinion gearing, or

page_text: tion, and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Alexander Crichton, do hereby declare
the nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement and accompanying Drawing:-
This Invention relates to a novel mode of removing the screw from between
the outer and inner stern posts of a screw steamer, and in the arrangement of
parts for effecting that object, as also to the means or method of closing
the opening between the two stern posts when the screw propeller is removed
therefrom, so as to enable the ship to be more readily and accurately steered,
and to prevent the retardation of the ship through the water common to
vessels when under sail having the screw opening unclosed.
- Instead of providing a trunk or well hole extending from the head of tho
screw space to the upper deck line, of a size necessary to admit of the passage
of the screw and frame, and also a bango frame with its fittings, as ordinarily
employed in the navy for lifting vertically the screw propeller on to the poop
or deck in vessels having inner and outer stern posts; and also instead of the
ordinary modes or methods of removing overhung propellers, or propellers which
project beyond the rudder; and instead also of any of the arrangements for
feathering the blades of screws, or otherwise moving or removing them, or
changing their position, for the purpose of enabling a ship to be sailed without
the obstruction offered to her passage through the water by the screw remaining
immersed therein, I construct the last length of screw shaft and the parts
and fittings in connection therewith in the following manner :-I connect the
last (or outer) length of shaft with a joint or coupling in the manner of a
binge, so that when the knuckles or faces of the joints stand vertically, the
shaft having the screw upon it may be raised from the horizontal to a vertical
position. The water-tight gland or stuffing box upon the screw shaft is in
advance of or forward of the joint or coupling, as is also the thrust block.
Suitable bearings are provided for the moveable length of screw shaft to rest
in when at work, and top brasses or bearings may be provided and be placed in
position when the shaft is lowered, and capable of being moved or withdrawn
horizontally or vertically when the screw and its shaft have to be raised or
withdrawn. The last length or piece of propeller shaft need only be of a
length sufficient to enable the point of the lower blade of the screw to come
within the line of the inner stern post when the screw shaft is vertical and
the screw horizontal; but the screw shaft may be turned up to an extent less

page_text: ordinary block and fall tackle; or any other well-known mechanical means.
may be employed for giving the requisite amount of motion, and for securing
the propeller when raised. For the purpose of closing the opening or void
left by the screw propeller when it has been withdrawn, or out of use, 1 provide
a continuation of the space or opening upward to any convenient height, for
the purpose of containing a sliding shutter piece of such dimensions and form
as will enclose or fill up the opening or space between the outer and inner
sternposts. This sliding shutter piece may be raised or lowered by means of
a winch or barrel worked from the poop or deck, or in any other convenient
position, and as it is guided and supported throughout its entire height it is
readily brought into use or removed, and whilst lowered for the purpose of
closing the opening it remains firm and free from motion, and strengthens and
prevents the undue straining of the outer sternpost, whilst it also enables the
rudder to act efficiently when the ship is under canvass.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filcil
by the said Alexander Crichton in the Great Seal Patent Office on the
31st July 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
CRICHTON, of Cork, Superintending Engineer of the Cork Steam Ship Com-
pany, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the First day of February, in the year of our Lord One
thousand eight hundred and sixty-one, in the twenty-fourth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Alexander Crichton, Her special licence that I, the said Alexander Crichton, my
executors, administrators, and assigns, or such other as I, the said Alexander
Crichton, 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
APPLYING AND FITTING SCREW PROPELLERS, AND IN FORMING AND FITTING THE
STERN PARTS OF SHIPS FOR RECEIVING SCREWS," upon the condition (amongst
others) that I, the said Alexander Crichton, my executors or administrators,
by an instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said Inven-

page_text: or more than ninety degrees from its original plane of rotation for the purpose
of accommodating any feature in the internal arrangement of the stern of the
ship. For the purpose of enabling the screw shaft to be raised as described,
as also for the purpose of allowing the screw propeller to be raised and moved
inward by describing a quadrant or any lesser or greater portion of a circle,
I divide the inner sternpost from the boss upwards into two parts or thicknesses,
leaving the requisite space between them, and I form a box or hollow space
immediately above the narrower part of such opening for the purpose of
receiving the screw. Where it is desirable to provide for the removal or
renewal of the screw propeller, or its adjustment, examination, or repair, it is
only necessary to continue this water-tight or boxed space up to any convenient
height above the deep load water line to enable ready access to be afforded to
the scrow and its shaft. Power may be applied to the screw shaft for the
purpose of raising or moving it in the manner described, either by means of a
rack and pinion gearing, or ordinary block and fall tackle, or any other well
known mechanical means may be employed for giving the requisite amount of
motion, and for securing the propeller when raised. For the purpose of
closing the opening or void left by the screw propeller when it has been with-
drawn or out of use, I provide a continuation of the space or opening upward
to any convenient height for the purpose of containing a sliding shutter piece
of such dimensions and form as will enclose the opening or space between
the outer and inner stern posts. This sliding shutter piece may be raised or
lowered by means of a winch or barrel worked from the poop or deck or in
any other convenient position, and as it is guided and supported throughout its
entire height it is readily brought into use or removed; and whilst lowered
for the purpose of closing the opening it remains firm and free from motion,
and strengthens and prevents the undue straining of the outer sternpost, whilst
it also enables the rudder to act efficiently when the ship is under canvass.
In the accompanying Sheet of Drawings I have illustrated the application of
my Invention to a screw steam ship more particularly intended for commercial
purposes.
Figure 1 shows a cross section of a screw. steamer taken through the centre
of the screw shaft when raised up; Figure 2-is-a longitudinal section taken
through the centre of the vessel at the stern end. In each of these Figures
the same letters are used to indicate corresponding parts.
A is the hull of the ship; B, the after sternpost; C, the forward sternpost;
D, the rudder; E, the narrow vertical opening or trunk, which need only be
of sufficient thickness to permit of the sliding door or shutter passing up and
down freely; F the chamber formed in the stern of the ship for the purpose

page_text: of enabling the screw to be drawn thereinto or housed, as shown and
described.
The lower part or portion of this chamber, marked F', need only be of a.
width sufficient to enable the piece of screw shaft a, a, a, to move radially
therein.
a, a, a, is the aftermost piece of screw shafting, with the propeller attached;
it is connected at the fore end to the next length of shafting by a joint or
coupling b, formed like a hinge, so that it can be raised into the position.
shown in the Drawing; or lowered when desired, without disconnecting the
shafts; c, c, c, represents the chamber formed by the division of the inner stern
post, and serving as a quadrantal guide, in which the piece of shafting a
works; d, d, is a long bar or strut, screwed and working into a nut e, the
lower end fitting into the cup f, (which is attached to the upper half of the
inner stern post, bush, or pipe), and keeping the screw shaft and propeller in
their places when the machinery is at work. The propeller and the piece of
shafting a, a, a, may be lowered into its working position (as shown by the
dotted lines) from the position in which it is shown by full lines in the
Drawings; h, h; is a door or shutter fitted to work up and down betwixt
the stern posts, and which when the propeller is at work is readily raised up
out of the way.
I am thus enabled by the introduction of the sliding door or shutter in
manner herein-before set forth, and as illustrated in the accompanying Drawing,
to secure that a very considerable portion of the water which in screw steam
ships not having this provision would pass through the outer and inner stern
posts is, according to my Invention, made to pass towards the rudder, when a
screw steamer is under canvass especially when "sailing on a wind," and
thereby greatly improving the vessel's steering qualities.
Although I have shewn in the accompanying Drawing an arrangement of
parts and mode of fitting and working screw propellers in accordance with my
present Invention, yet I wish it to be understood that I do not confine myself
to the exact proportion of the several parts, nor to the precise arrangement
and disposition thereof, as they must in each case be varied to adapt them to
the particular class of vessel, and the form and nature of the after part of the
ship to which the Invention has to be applied; but what I claim is --
First, the mode or method herein described of removing from betwixt the outer
and inner stern posts the screw propeller, together with the aftermost piece of
screw shafting, for the purpose of enabling the space between the stern posts
to be closed by means of a vertically sliding door or shutter, applied in manner
shown, and as herein described.

page_text: Second, the mode or method of constructing or forming the after part of
screw steam ships, as herein described, for the purpose of enabling screw
propellers to be hauled up or removed from between the stern posts when the
ship is required to sail under canvas, as well as for the purpose of examining,
repairing, readjusting, or removing and replacing screw propellers (and the
outer length of screw shaft) without the necessity for docking the ship.
Third, the novel mechanical contrivance and arrangement herein described,
and shewn in the accompanying Drawing, by which a screw propeller and a
portion of the screw shaft, may be securely held in position whilst at work,
and be readily removeable, or capable of being drawn up, or removed from
between the forward and after stern posts, either for the purpose of sailing the
ship, or for the purpose of more readily examining or operating upon the screw
or its shaft when desired.
In witness whereof, I, the said Alexander Crichton, have hereunto set
my hand and seal, this Twenty-sixth day of July, One thousand eight
hundred and sixty-one.
Witness,
MICHAEL HIGGINS,
of Cork.
ALEXANDER CRICHTON. (L.S.)