IMPROVEMENTS IN PROPELLING VESSELS
Year: 1844

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
BENNET WOODCROFT, of Manchester, in the County of Lancaster,
Consulting Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria,
by Her Letters Patent under the Great Seal of Great Britain,
bearing date at Westminster, the Thirteenth day of February now
last past, did, for Herself, Her heirs and successors, give and grant
unto me, the said Bennet Woodcroft, my exors, adññiors, and
assigns, Her especial licence that I, the said Bennet Woodcroft,
my exors, adñiors, and assigns, or such others as I, the said
Bennet Woodcroft, my exors, admors, or assigns, should at any
time agree with, and no others, from time to time and at all
times during the term of years therein expressed, should and
lawfully might make, use, exercise, and vend, within England,
Wales, and the town of Berwick-upon-Tweed, any Invention of
"IMPROVEMENTS IN PROPELLING VESSELS," in which said Letters Patent
is contained a proviso, obliging me, the said Bennet Woodcroft, by
an instrument in writing under my hand and seal, particularly to
describe and ascertain the nature of the said Invention, and in what

page_text: manner the same is to be performed, and to cause the same to be in-
rolled in Her Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said recited
Letters Patent, as in and by the said Letters Patent, reference being
thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the
said Bennet Woodcroft, do hereby declare the nature of my said In-
vention to consist,―
First, in such a combination of the blades of what are usually called
screw propellers, or of blades which act in the water as screw propellers,
with other suitable apparatus, as will, when required, enable the angle
such blades form with the driving shaft or axis upon which they are
placed, to be changed from a less angle to a greater, or from a greater
angle to a less, so that the best pitch of the blades may thereby be
obtained for driving the vessel under varying circumstances, such as
alterations in the speed of the vessel, in the depth of its immersion in
the water, and in the current of water or wind, or of both, in which it is
acting. Secondly, in the combination of apparatus with the blades, by
which they are held to any required angle with the driving shaft upon
which they are placed, or are moved from one angle to another, so as
thereby to alter their pitch. And lastly, in the combination of an indi-
cator, with the above mentioned apparatus and blades, so constructed as
at all times to shew at what pitch the blades then are, or as nearly so as
in practice is required. The nature of my said Invention will admit of
its being applied to a screw propeller having any required number of
blades, and such blades may be of any shape or dimensions capable of
being moved, so as to alter their pitch as much as is required to obtain
the best results from the screw; but I prefer blades of increasing pitch
(whatever be their form in other respects) such as I previously invented,
and for which I obtained Letters Patent for England on the Twenty-
second day of March, One thousand eight hundred and thirty-two.
Blades of screw propellers made on the increasing pitch are now so well
known and understood by persons conversant with the making of screw
propellers, that it is not needful here to explain their mode of construc-
tion. The nature of this my Invention will also admit of the blades

page_text: the apparatus by which the pitch is regulated, and the indicator, being
placed in any suitable part of the vessel.
Having now described the nature of my said Invention, I shall pro-
ceed to shew the manner in which the same may be performed by the
following description, reference being had to the Drawings annexed, and
the figures and letters marked thereon. The same letters denote the
same parts throughout the Drawings. Figure 1, represents a portion
of a steam vessel, with the whole of my improvements attached
thereto. Figure 2, represents an end view of the groove box which
slides upon and turns round with the shaft, and also the cranked lever
and part of the rod by which such box is slid backwards or forwards
upon the shaft to the required distance. Figure 3, represents an end
view of the screw shewn in Figure 1. Figures 4, 5, and 6, shew one
of the blades of the screw with an arm attached at the lower extremity
in three different positions. Figure 7, shews the periphery of the
middle blade shewn in Figure 1, at three different angles to the driving
shaft or axis upon which it is placed, each of the angles being shewn
in a different colour. All the above mentioned Figures are drawn upon
the scale shewn in the Drawings. When the periphery of each blade of
the screw is at the angle shewn by the blue line in Figure 7, the blades
will then be at or nearly at a seven and a half feet pitch; and, provided
no slip or recession of the water were to take place by the screw being
turned in the water at the rate of one hundred revolutions per minnte,
the screw would in an hour's time have passed through a distance of
eight miles and nine hundred and twenty yards or thereabouts. When
the periphery is at the angle shewn by the black line, the blades will
then be at or nearly at an eleven feet pitch; and provided they were
turned at one hundred revolutions per minute, and provided also that
no slip or recession of the water were to take place, the screw at that
pitch would in an hour's time have passed through a distance of twelve
miles and a half or thereabouts. And when the periphery is at the
angle shewn by the red line, the blades will then be at or nearly
at a fourteen and a half feet pitch;
same circumstances as to speed and as to the water as in the two
preceding cases, the screw would in an hour's time have passed
and if they were turned under the

page_text: through a distance of sixteen miles and eight hundred and forty
yards or thereabouts.
In Figure 1, A, B, C, D, represent portions of a vessel; the part
'marked A, being the stern post of the vessel; the part marked B,
being the portion of the vessel projecting beyond the stern post and over
the opening in which the screw is placed; the part marked C, is a
false stern post; and the part marked D, is a continuation of the keel
extending under the screw from the real to the false stern post. E, is
a piece of iron which passes on each side of and is united to the pieces
A, C, and D, to keep them fixed in their places. F, is the driving
shaft upon which the screw and the grooved box are placed. This shaft
extends from a bearing or step attached to the false stern post C, and
through a stuffing box in the stern post A, to the driving geer or
engine by which it is turned. a, is a boss keyed fast upon the driving
shaft, which has four projecting bearings cast upon it, two of which
only are seen in Figure 1, marked b. These bearings form an angle
with the driving shaft corresponding in some measure with the angle
formed by the bottoms of the blades of the screw, which blades they
have in part to hold. The outside of each bearing is made in a convex
form, with a hole cut through it of sufficient size to admit of the arm d,
attached to the shaft of the blade to pass through it, and to traverse
sideways as much as is required to alter the pitch of the blade; and the
inside is made with a semicircular slot in it, which, with a correspond-
ing slot in the cap c, forms a circular bearing or step for the shaft at
the bottom of the blade. When the arm d, and the blade e, are put in
their places, the cap c, is bolted to the fixed bearing b, and it thereby
secures the blade in its working position. The outside of the cap
is convex, and is in that respect similar to the outside of the
fixed hearing. f, is a grooved box placed upon the driving shaft
F, which shaft has two fixed keys, g, let into it, running in
the direction of its length, one on each side. The box f, is placed
over these keys, and it has two slots or key
inside, shewn in Figure 2, in which the fixed
enter, and by which when the shaft is turned round
grooves h, in the
keys on the shaft
the box is turned
round also; but these slots and keys do not prevent the box from

page_text: being slidden backwards or forwards on the shaft. On the outside of
this box are four oblique grooves i, which receive the circular heads of
the studs. The narrower parts of these studs pass through circular
openings k, (see Figure 6,) in the end of the arms d. 1, is a slot passing
round the box f, into which two studs m, project (see Figure 2,) fixed
to the two lower extremities of the bell crank levers n.. These levers
work upon centres at o. The pin, which passes through the levers and
to which they are keyed, works in a bearing of the bracket p, which is
attached to the stern post of the vessel. Two links q, unite the bell
crank levers to the cross head 2. Through this cross head r, the rods,
passes, and it is so attached to that cross head as to turn freely round
in it, or to move it up and down as required. The upper part of this
rod passes through the deck, the line of which is shewn at G, and
through a short column I, fixed on the deck; part of the rod which
passes through this column has a worm cut into it so as to form a
screw which works in a nut y, fixed inside the column H. On the top
of the rod s, is fixed a wheel, with handles by which the rod s, can be
turned. 2, is an indicator with a number of teeth placed concentric
with its axis on the one side, and having on the other a finger and index
plate shewing at what pitch the screw is. This column H, and the in-
dicator, are best shown on an enlarged scale at Figure 8. a, is a case
which rests upon the worm on the rod s, with a pin passing through the
rod over the case. This case has a rack on one side, in which work the
teeth of the indicator z. W, is a key fixed to the column, which takes
into a groove behind the case x, and which prevents the case from
turning round. When the wheel at the top of the rod s, is turned so
as to force the rod down, it will, by its action upon the links and bell
cranks, force the sliding box on the shaft nearer to the screw, and the
oblique grooves in the box acting upon the arms of the screw will turn
the blades to a less angle with the axis, and thereby decrease the pitch
of the screw; and when the wheel is turned so as to draw the rod up,
it will, by its action upon the links and bell cranks, draw the sliding
box further from the screw; and the oblique grooves in the box acting
upon the arms of the screw will turn the blades to a greater angle with

page_text: the axis, and thereby increase the pitch of the screw. It will be obvious
that when the rod s, descends or ascends by the screw upon it the case
a, also descends or ascends with it, and the rack upon it thereby moves
the finger of the indicator over that part of the plate of the indicator
which shews at what pitch the blades of the screw then are.
Having now described the nature of my said Invention, and the
manner in which I carry it into effect,-
I declare that I do not claim any of the parts separately which I
have used in my improvements in propelling vessels.
But I do claim as of my Invention the combination of the blades
of screws, or blades which act as screws, with other apparatus, by which
the pitch of such blades may be altered at pleasure, and indicated, as
herein-before described.
And this my Invention being, to the best of my knowledge and
belief, entirely new, and never before used within that part of Her
said Majesty's United Kingdom of Great Britain and Ireland called
England, Her dominion of Wales, or town of Berwick-upon-Tweed,
I do hereby declare this to be my Specification of the same, and that
I do verily believe this my Specification doth comply in all respects
fully and without reserve or disguise with the proviso in the said herein-
before in part recited Letters Patent contained.
Wherefore I do hereby claim to maintain exclusive right and privi-
lege to the said Invention.
In witness whereof, I, the said Bennet Woodcroft, have hereunto
set my hand and seal, the Twelfth day of August, in the year of
our Lord One thousand eight hundred and forty-four.
BENNET (L.s.) WOODCROFT.
Signed, sealed, and delivered (being
first duly stamped) by the within-
named Bennet Woodcroft in the

page_text: AND BE IT REMEMBERED, that on the Twelfth day of August,
in the year of our Lord 1844, the aforesaid Bennet Woodcroft came
before our said Lady the Queen in Her Chancery, and acknowleged
the Specification aforesaid, and all and every thing therein contained
and specified in form above written; and also the Specification aforesaid
was stamped according to the tenor of the statute made for that purpose.
Enrolled the Thirteenth day of August, in the year of our Lord
One thousand eight hundred and forty-four.