Improvements in and relating to Ships' Propellers.
Year: 1891

page_text: Date of Application, 1st Jan., 1891
Complete Specification Left, 1st Oct., 1891-Accepted, 14th Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in and relating to Ships' Propellers.
I, JAMES JAQUES of 38 Kerbey Street, Poplar E., Boiler Maker, do hereby
declare the nature of this invention to be as follows:-
My invention is devised with a view to increase the efficiency or thrust of the
marine screw propellers and to minimise the loss in propelling power due to the
presence of back flow or dead water, and, from slip.
The essential feature in the improvements according to my invention consists in
the propeller blades being formed near the end thereof with, or having adapted
thereto, a protuberance or cap piece either hollow or solid on the after side of each
of the blades. I propose that the external configuration of said cap pieces shall
assume a form say prismatic or otherwise such as will ensure the obtainment
of a wedge like action upon the water when the improved screw propeller is at
work. I may also with a view to assist the propelling power cause said improved
propellers to fulfil, to a certain extent, a hydropropulsive function. That is to
say the caps or protuberances aforesaid would assume the form of hollow shell
pieces provided with cavities which would become partly self loading, the water
entering on the falling blades and discharging on the rising blades.
Dated this 1st day of January 1891
JAMES
STEVENSON,
Gray's Inn Chambers, 20, High Holborn, W.C., Agent for Applicant.
COMPLETE SPECIFICATION.
Improvements in and relating to Ships' Propellers.
I, JAMES JAQUES of 38 Kerbey Street, Poplar E., Boiler Maker, do hereby
declare the nature of this invention and in what manner the same is to he
performed, to be particularly described and ascertained in and by the following
statement:-
My invention is devised with a view to increase the efficiency or thrust of marine
screw propellers and to minimise the loss in propelling power due to the presence
of back flow or dead water and from slip.
The improved propellers according to my invention may have two, three or
more blades.
My improvements are illustrated in the accompanying sheet of
drawings by front and side elevational views at Figures 1 and 2 respectively,
Figures 3 and 4 being detached views to be hereinafter referred to.
In carrying out my invention I either cast on with, or afterwards affix to, the
blade, a protuberance A, disposed, as shewn, towards the peripheral edge of blade.
Said protuberance A assumes the configuration of a six or more sided frustrum of
a pyramid or prism with truncated apex a the centre of which is situate preferably
slightly out of the longitudinal central line of blade. In Figures 1 and 2, A is
shewn as forming part of or being cast with, the blade; whereas, the detached
views Figures 3 and 4 illustrate the case in which said protuberance A is rivetted
on as at band or otherwise affixed to an existing propeller blade, and in said
case (referring to Figures 3 and 4) the attachments A may be made of sheet steel,
iron, copper or any other metal.
The resultant advantages of the improvement herein described and illustrated are
that practically, the pitch of the outer edge of propeller blade is increased for
going ahead and at that portion of the blade which is most effective, thus getting
rid of the "churning" action due to having a coarse pitch at the boss, owing to

page_text: the blade at boss being more nearly square to the shaft, thus diminishing the waste
of power at that part, as the pitch is increased at the outer part formed by the
angulated sides of the protuberance A.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is
In marine screw propellers a protuberance such as A, either forming part of,
and in one with, the propeller blade, or, as a separate attachment thereto, sub-
stantially as and for the purposes herein set forth.
Dated this 1st October 1891.
JAMES
STEVENSON,
Gray's Inn Chambers, 20, High Holborn, W.C., Agent for Applicant.