Year: 1886

page_text: I ALFRED FERNANDEZ YARROW of the firm of Yarrow and Company of the Isle
of Dogs Poplar Shipbuilders do hereby declare the nature of this Invention to be
as follows:-
This Invention relates to the class of propellers wherein the screw is encased or
partly encased in a tube the rotary motion imparted to the water by the screw
being utilized by means of guide blades so as to produce propelling effect With
this form of propeller it has been found that there is great difficulty in going
astern and it is the object of my Invention to overcome this difficulty-According
to my Invention I affix guide blades forward of the screw as well as aft of it.
These blades I prefer to be situated in planes radiating.from the centre line of the
shaft so that they do not cause resistance when going ahead I find that the said.
extra blades, whilst causing practically no reduction in efficiency in going ahead
give a greatly increased efficiency when going astern.
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.,
Agent for the said A. F. Yarrow.

page_text: I, ALFRED FERNANDEZ YARROW, of the firm of Yarrow and Company of the Isle
of Dogs, Poplar, Shipbuilders 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 the class of propellers wherein the screw is encased or
partly encased in a tube and the efficiency of it augmented by means of guide
blades or surfaces aft of the propeller so as to increase the propelling effect. With
this form of propeller it has been found that there is great difficulty in going
astern and it is the object of my Invention to overcome this difficulty. According
to my Invention I affix guide blades or surfaces forward of the screw as well as
aft of it. These blades or surfaces I prefer to be situated in planes radiating from
the centre line of the shaft so that they do not cause resistance when going ahead.
I find that the said extra blades or guiding surfaces whilst causing practically
no reduction in efficiency in going ahead give a greatly increased efficiency when
going astern.
In the accompanying drawing Figure 1 is a longitudinal elevation of the after
part of a steam vessel fitted with a propeller provided with guide blades according
to my Invention and Figures 2 and 3 are respectively an end elevation and a plan
of the propeller and guide blades. The boss A carrying two three or more
propeller blades B is fixed to the propeller shaft C and revolves within the
cylindrical casing D. The continuations of the boss A. forward and aft of the
propeller are fixed to the casing D by means of a number of guide blades E and F
situated both forward and aft of the propeller.
These guide blades E and F may be radial and not curved but straight in a fore
and aft direction so that their effect on the stream coming from the propeller
whether either ahead or astern is to prevent rotary motion of the water on leaving
the apparatus.
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
In propellers of the kind referred to (namely propellers encased or partly
encased in a tube) the combination with the propeller of guide blades or guide
surfaces situated both forward and aft of the said propeller substantially as
hereinbefore described.