IMPROVEMENTS IN SCREW PROPELLERS FOR SHIPS AND OTHER NAVIGABLE VESSELS
Year: 1874

page_text: LETTERS PATENT to William George Rothwell, of Liverpool, in the
County of Lancaster, Master Mariner, for the Invention of
"IMPROVEMENTS IN SCREW PROPELLERS FOR SHIPS AND OTHER NAVIGABLE
VESSELS."
Sealed the 13th May 1875, and dated the 27th November 1874.
PROVISIONAL SPECIFICATION left by the said William George
Rothwell at the Office of the Commissioners of Patents, with his
Petition, on the 27th November 1874.
I, WILLIAM GEORGE ROTHWELL, of Liverpool, in the County of
Lancaster, Master Mariner, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN SCREW PROPELLERS FOR SHIPS AND OTHER
NAVIGABLE VESSELS," to be as follows:-
:―
The objects of this Invention are (1) to provide efficient and simple
means for securing and adjusting propeller blades on the boss, and (2)
to so construct propeller blades that (a) there shall be less slip when the

page_text: propeller is in action, (6) the vacuum behind the blades shall be reduced,
and (c) greater efficiency shall be secured.
To obtain the advantages first above mentioned I construct the boss
with an annular recess for cach blade; such annular-recess is wider at
the bottom than at the top, being preferably tee shaped. In the bottom
or widened portion of such recess a ring is fitted, and the blade is secured
to such ring by bolts. To allow of the ring being inserted into the said
recess part of the boss is removable.
It will be obvious that a blade.secured as above described can be
adjusted to any angle. Keys or similar means are provided to prevent
the blade from shifting when properly adjusted.
To secure the advantages second above mentioned I form each blade
of two or more bladelets preferably united at the top, and so dispose such
bladelets one behind the other that the second shall receive a second
thread of water, the third a third thread of water, and so on, as if the
first blade had been as broad as all the bladelets put together. The said.
bladelets are also so disposed that each bladelet partially destroys the
vacuum formed behind the preceding bladelet. The bladelets are pre-
ferably placed at a gradually increasing pitch.
When bladelets are arranged as above described a line joining the 1
leading edge of the first or leading bladelet and the rear edge of the
second or following bladelet will be parallel or nearly parallel to the
screw shaft. The same thing takes place with the other bladelets.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William George Rothwell in the Great Seal Patent 2
Office on the 27th May 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
GEORGE ROTHWELL, of Liverpool, in the County of Lancaster, Master
Mariner, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her 3
Letters Patent, bearing date the Twenty-seventh day of November, in
the year of our Lord One thousand eight hundred and seventy-four, in

page_text: the thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said-William George Rothwell, Her
special licence that I, the said William George Rothwell, my executors,
administrators, and assigns, or such others as I, the said William George
Rothwell, 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
SCREW PROPELLERS FOR SHIPS AND OTHER NAVIGABLE
VESSELS," upon the condition (amongst others) that I, the said William
George Rothwell, 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 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 William George Rothwell, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Sheet of Drawings and to the figures and letters marked thereon, that is
to say:―
3
The objects of this Invention are (1) to provide efficient and simple
means for securing and adjusting propeller blades on the boss, and (2)
to construct propeller blades that (a) there shall be less slip when the
propeller is in action, (b) the vacuum behind the blades shall be reduced,
and (c) greater efficiency shall be secured.
To obtain the advantages first above mentioned I construct the boss
with an annular recess for each blade; such annular recess is wider at
the bottom than at the top, being preferably tee shaped. In the bottom
or widened portion of such recess a ring is fitted, and the blade is secured
to such ring by bolts. To allow of the ring being inserted into the said
recess part of the boss is removable.
It will be obvious that a blade secured as above described can be
adjusted to any angle. Keys or similar means are provided to prevent
the blade from shifting when properly adjusted,

page_text: modification of bladelet, substantially as described and illustrated under
Fig. 6, for the purpose set forth.
In witness whereof, I, the said William George Rothwell, have
hereunto set my hand and seal, the Fifteenth day of May, in
the year of our Lord One thousand eight hundred and seventy-
five
WILLIAM GEORGE ROTHWELL. (L.S.)
Witness,
JAMES JOHNSON,
Patent Office,
4, Clayton Square,
Liverpool.