IMPROVEMENTS IN SCREW PROPELLERS
Year: 1870

page_text: LETTERS PATENT to Alexander Browne, of the Firm of Browne and
Company, Patent Agents, of 85, Gracechurch Street, in the City of
London, for the Invention of "IMPROVEMENTS IN SCREW PROPELLERS." ―
A communication from abroad by Cornelis Johannes Wilton Van
Reede, of Rotterdam, Holland.
Sealed the 22nd November 1870, and dated the 23rd May 1870.
PROVISIONAL SPECIFICATION left by the said Alexander Browne at
the Office of the Commissioners of Patents, with his Petition, on
the 23rd May 1870.
I, ALEXANDER BROWNE, of the Firm of Browne and Company, Patent
Agents, of 85, Gracechurch Street, in the City of London, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN SCREW
PROPELLERS," a communication from abroad by Cornelis Johannes Wilton
Van Reede, of Rotterdam, Holland, to be as follows:-
This Invention is designed to increase the speed of vessels propelled

page_text: it is to be driven, also to prevent or considerably lessen the slip and
vibratory motion attending screw propellers as heretofore constructed.
I propose to accomplish the above objects by constructing screw pro-
pellers in the following manner, that is to say:- -Instead of forming the
blades of the screw on one solid boss of metal with the blades ranging in
the same vertical plane around the said boss as now practised, I propose to
form each blade on a separate boss and arrange the said blades one
behind the other on the driving shaft. The two outer blades are keyed
firmly on the said shaft, and the central blade is held firmly in position
by its boss clutching or locking into the bosses of the other two blades;
by these means should one or other of the blades be broken, instead of
all three of the blades having to be thrown away, the broken blade only
need be removed. By this improved propeller I am enabled with less
diameter and surface of blades, and fewer revolutions of the screw shaft
to obtain greater speed of a vessel to which such said screw propeller
may be applied.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Browne in the Great Seal Patent
Office on the 23rd November 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
BROWNE, of the Firm of Browne and Company, Patent Agents, of 85,
Gracechurch Street, in the City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-third day of May, in the year of
our Lord One thousand eight hundred and seventy, in the thirty-third
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Alexander Browne, Her special licence
that I, the said Alexander Browne, my executors, administrators,
and assigns, or such others as I, the said Alexander Browne, adminis-
trators, 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

page_text: Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN SCREW
PROPELLERS," a communication from abroad by Cornelis Johannes Wilton
Van Reede, of Rotterdam, Holland, upon the condition (amongst
others that I, the said Alexander Browne, my executors or adminis-
trators, 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 Invention, 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 Browne, do hereby
declare the nature of the said Invention, and in what manner the same
(is to be performed, to-be particularly described and ascertained in and
by the following statement, that is to say :-
This Invention is designed to increase the speed of vessels propelled
by screws without increasing the size of the screw, or the speed at
which it is to be driven, also to prevent or considerably lessen the
slip and vibratory motion attending screw propellers as heretofore
constructed.
I propose to accomplish the above objects by constructing screw
´propellers in the following manner, that is to say :--Instead of forming
the blades of the screw on one solid boss of metal with the blades
ranging in the same vertical plane around the said boss as now practised.
I propose to form each blade on a separate boss and arrange the said
blades one behind the other on the driving shaft. The two outer blades
are keyed firmly on the said shaft and the central blade is held firmly
in position by its boss clutching or locking into the bosses of the other
two blades, by these means should one or other of the blades be broken,
instead of all three of the blades having to be thrown away t the broken
blade only need be removed. By this improved propeller I am enabled
with less diameter and surface of blades and fewer revolutions of the
screw shaft to obtain greater speed of a vessel to which such said screw
propeller may be applied.
And in order to explain this Invention more completely I now
proceed to describe the best means I am in possession of for carrying
the same into practical effect, reference being had to the illustra-

page_text: Figure 1 represents a side elevation of a screw propeller shewing the
construction of the blades and the method of connecting them together
upon the propeller shaft; Figure 2 is an end elevation of Figure 1. At
each of the above Figures similar letters of reference are placed upon
corresponding parts.
A marks a metal frame to be fixed to the stern of a ship or in that:
part of a wooden ship called the dead wood; B is the propeller shaft;
C, brass or gun metal bearing employed to support the outer end of the
propeller shaft around which the screw blades are arranged and fixed
as presently described; D is a long brass or gun metal bearing to support
the propeller shaft in the frame A; E, G, H, mark three screw blades,
each formed with a boss I formed as a clutch so as to take or lock one
into the other. The aforesaid bosses are turned or bored taper or conical
and the part of this part of the shaft B on which the bosses are to fit
is also turned of the same taper as the holes in the said bosses, so that
when the said blades are placed by their bosses on the shaft A and the
boss I of the blade E is fixed by a key to the shaft A, all the blades
will rotate with the propeller shaft, and this applies to small screws.
For large screws it is proposed to key the boss G to the shaft as well as
the boss E.
The amount of pitch of the screw which has been found answer well
in practice is as follows:-If the screw is 4 feet in diameter, the pitch
should be five feet. When it is desired to retain the same speed that
the propeller shaft has been driven when working a screw of the ordinary
construction the increase of speed may be obtained by the use of the
above described improved propeller by simply decreasing the pitch of
the screw.
Having now fully described and set forth the nature and object of
this Invention for " Improvements in Screw Propellers" and the means
by which it may be effected, I hereby declare this Invention to consist
in and I claim constructing, arranging, and connecting together and to

page_text: the propeller shaft the blades of screw propellers as above described
with reference to the accompanying Drawing.
In witness whereof, I, the said Alexander Browne, have hereunto
set my hand and seal, this Twenty-third day of November, in
the year of our Lord One thousand eight hundred and seventy.