Improvements in Screw Propellers.
Year: 1897

page_text: Date of Application, 27th Aug., 1897-Accepted, 30th Oct., 1897
Improvements in Screw Propellers.
I, LAWRENCE HARDIE DRAKE, 36, King William Street, Greenwich, Marine
Surveyor, 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 improvements in connection with screw propellers
for vessels and its object is to provide a propeller which will work with a uniform
pressure and which will not be liable to slip.
When propellers of the ordinary kind having three or four blades are employed
there is considerable slip as one blade follows in the trough formed by the one
in front of it resulting in great loss of power.
In carrying out my invention I propose to place the blades in different planes
so that in the case of four bladed propellers two of the blades will be directed
towards the front and two to the rear.
Owing to this arrangement the blades will obtain a proper grip on the water as
each will have a solid body of water in front of it. The advantages of the two
bladed propeller are thus obtained together with the steadiness resulting from
the use of a larger number of blades.
In order that the invention may be more clearly understood reference is had to
the accompanying drawing which shows my improved propeller in side elevation.
A is the boss of the propeller carried on the shaft B. and carrying the blades C
and C. These are arranged in two pairs C being directed towards the front
and C towards the rear. The blade shown in dotted lines at the upper part of
the drawing indicates the position of one of the blades C¹ when it reaches the
top. It is thus clearly seen that the blades C and Care now in a different plane
and will not be liable to interfere with each other. The rear blades miss tho
trough produced by the front ones. The drawing shows a solid propeller in which
the blades are formed in one piece with the boss, but the arrangement is equally
applicable to propellers formed in parts having the blades bolted to the central
boss. Propellers constructed in this manner not only decrease the slip but also
lessen the vibration and largely increase the speed of the vessel. The arrange-
ments has been shown applied to the four bladed propeller but it is also applicable
to a propeller having three blades. These propellers can be fitted to existing
vessels as the ordinary propeller wells leave enough space to allow of these blades
being fitted and there is no need to alter the end of the shaft. In the case of twin
screws blades can be set at any angle.
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:-
:-
1. An improved screw propeller for vessels having the blades set in different
planes substantially as and for the purposes specified.
2. In an improved screw propeller for vessels having four blades, forming the

page_text: blades in two pairs, one pair being directed towards the front and the other towards
the back substantially as and for the purposes specified.
3. An improved screw propeller for vessels having two pairs of blades situated
in different planes and operating substantially as described and shown in the
drawing and for the purposes spécified..
GEO. H. RAYNER
37, Chancery Lane, London, Agent for the Applicant.