Improvements in the Blades of Screw-propellers.
Year: 1896

page_text: Date of Application, 22nd Dec., 1896-Accepted, 20th. Feb., 1897
COMPLETE SPECIFICATION.
Improvements in the Blades of Screw-propellers.
I, FREDERICK WITTRAM, of No. 2319 California Street, in the City and
County of San Francisco, State of California, United States of America,
Gentleman, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
My invention relates to improvements to be applied to propellers for vessels and
other similar purposes. It consists in a novel construction of the propeller blade
having corrugations decreasing in depth transversely from the front to the rear
edge of the blade.
Referring to the accompanying drawing, the figure is a view shewing a blade
of my propeller.
The object of my invention is to provide a propeller with blades, one of the
edges of each of which is corrugated or formed in planes or surfaces having such
an angle or curvature with each other as to form a greater surface than the actual
length to impinge against the water through which the blade is travelling, said
corrugations or inclines decreasing in depth so that the other edges of the blade
are less corrugated or irregular, or it may be straight in a radial line from the
hub, or curved therefrom, thus concentrating the water as it passes over the blade
from one side to the other in the manner of a converging trough and greatly
strengthening the blade.
My propeller blade is formed with surfaces A inclining alternately to and from
each other so that one edge of the blade presents a form of inclined planes or
curved surfaces united to form a zig-zag or corrugated line from the hub to the
outer end of the blade.
From this edge, these inclines become shallower transversely and approach more
nearly to a straight or smooth line so that the opposite edge of the blade may be
nearly or quite straight.
This construction gives, first, great stiffness to the propeller blade by reason of
the bracing which each of the angular inclined or curved faces receives from the
other, in conjunction with the diagonal or transverse decrease in the depth from
one edge to the other edge. The channels or valleys thus formed in the blades
also decrease and converge from one edge to the other, so that the body of water
which engages the front portion of the blade during its revolution will be
discharged more rapidly through the converging transverse channel.
It will be understood that these blades may be of any suitable or well known out-
line, either converging from the hub toward the outer end, or diverging to any
desired degree, and the pitch or angle of the blades may be also determined to
suit the conditions under which the propeller is to be used.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. A propeller consisting of radial blades, the edges of which are composed of
inclined planes meeting each other at an angle to form a zig-zag line, said planes
do the
site adeo of the blade

page_text: 2. In a propeller, blades extending radially from the hubs with an appropriate
pitch, one of the edges of said blades being smooth.or slightly irregular, and the
other edge forming zig-zag lines caused by the meeting of oppositely inclined
surfaces whereby transverse valleys are formed, decreasing in depth from one edge
towards the other edge of the blade.
For the Applicant,
GEDGE & FEENY,
60 Queen Victoria Street, London, E.C., Chartered Patent Agents.