Year: 1897

page_text: We, ELIAS BAGGSTROM, Engineer; WILLIAM PHILIP GUTHRIDGE, Mining Agent;.
and ARTHUR EDWARD LANGLEY, Mining Agent; all of the City of Auckland, in
the Provincial District of Auckland, and Colony of New Zealand, 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 :-
This invention relates to an improved screw propeller blade for driving ships,
boats and vessels through water; the object of the Invention being to avoid the
churning of the water caused during the action of screw propellers having blades
formed in the manner hitherto in use, which is detrimental in that the water
radially dispersed by the centrifugal action generated by the revolution of the
inner parts of the working surface of the propeller blades interferes with the
desired action of the more outward parts of the working surface thereof, to the
consequent loss of efficiency in the propelling action of the screw; and also to
avoid the carrying of backwater by the propeller, by so shaping and forming the
propeller blade as to cause every part of its surface to work in water undisturbed
by centrifugal action and to thrust against the water directly rearwardly,
whereby, power will be economised and either an actual increase of speed attained
with a given consumption of fuel, or a saving of fuel effected in attaining a given
speed.
On the accompanying drawings:-
:-
Fig. 1, represents an end perspective view of a screw propeller having three of
the improved blades.
Fig. 2, is a plan view of the improved blade, showing the convex side, that
being the striking or working side of the blade, the line D, E, representing the .
centre line of the propeller.
Fig. 3, is an elevation and end view of the blade, showing the pitch and curve
thereof, and a portion of the upper part of the concave side thereof.
Fig. 4, is a side and partly front view of the blade, presenting the greater
portion of the convex or striking side thereof.
Fig. 5, is a full view of the convex or striking side of the blade; and
Fig. 6, is a full view of the concave or non-striking side of the blade.
A, represents the blade, which may, as represented, be formed with a flange B,

page_text: by which it may be bolted to a boss C, or, the blade may be otherwise conveniently
secured to the boss, or the blades may be cast integral with the boss.
To the end aforesaid, the present improvement consists in the peculiar shape and
conformation given to the propeller blade, which differ from those of existing
propeller blades in the following particulars, that is to say:-whereas, in all
forms of screw propellers hitherto in use, each blade is arranged in a position such
that the medial line of its working surface stands out from the hub in a direction
radially to the circumference of the propeller shaft, or, the said medial line is
curved backwards or forwards in, or closely approximating to, the plane passing
through the propeller shaft, and in which plane the said medial line of the blade
springs from the hub; the surface of the improved blade, as generated by the
position of the medial line, the pitch, and curvature backward or forward longi-
tudinally to the axis of the shaft as hitherto in use, is, in addition, curved or set
backward in the direction of rotation, or circumferentially to the propeller shaft.
This curvature, herein called the circumferential curve, is preferably regular, and
may be circular, parabolic, or made up of parts of regular or irregular curves.
The amount of this circumferential curve will vary according to the pitch and
general design of the propeller.
The effect of such circumferential curve or set of the blade backward in the
direction of revolution is that every part of the surface of the blade is caused to
work in water undisturbed by centrifugal action or by any other part of the
surface of the blade and with a directly rearward thrust, whereby, power is
economised and the advantages above referred to are attained.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what I
claim is:-
A propeller blade having its helical surface curved backwards in the direction of
rotation or circumferentially to the propeller shaft as hereinbefore described and
illustrated by the accompanying drawings.
1007
DAY, DAVIES & HUNT,
Chartered Patent Agents, 321, High Holborn, London, W.C.,
Agents for the Applicants.