IMPROVEMENTS IN SCREW PROPELLORS
Year: 1884

page_text: I, WILLIAM HAMILTON KINDERSLEY BRADFORD of Windsor in the County of
Berks, and of 35 Southampton Buildings, Chancery Lane, in the County of
Middlesex formerly Major in the 108th Regiment do hereby declare the nature
of my invention for "IMPROVEMENTS IN SCREW PROPELLORS" to be as follows:-
My invention relates to screw propellors ordinarily used for propelling vessels
and it has for its object a novel method of forming such propellors so that their
effective power is increased as compared with screw propellors as ordinarily
heretofore made, without any increase of the space occupied by them in the
direction of the length of the vessel
In ordinary screw propellors, a cylindrical or other boss is fitted and fixed upon
the driving shaft, and the blades of the screw are formed or fixed upon this boss,
their root or the part where they join the boss being at an angle with the centre
line of the shaft corresponding with the pitch of the screw.
In order to put my present invention in operation I make a double or compound
boss separated by a plane passing through the axis of the screw, and each part
being fixed upon the shaft not parallel with the latter but at an angle proportioned
to the pitch of the screw, so that the two parts of the boss also form an angle with
each other.
A blade is formed upon or attached to each part of the compound boss described
and by the method of arrangement of the boss described, the line of junction with
the blade whilst remaining at the same angle as in screws as ordinarily made, such
angle depending upon the pitch of the screw, describes a larger segment of a circle
round the circumference of the boss and the axis of the shaft such line of junction
of each blade extending round half an entire circle or even more if desired, and the
two blades being opposite and alternate to each other, the blade passing round
and attached to one part of the compound boss forming an angle with the alternate
blade passing round and attached to the other part of the compound boss.
The parts of the compound boss not required for the attachment of the blades
as described may be cut away and made of such shape as to reduce as much
as possible the resistance to its passage through the water, or additional supple-
D

page_text: mentary blades may be formed or fixed upon other parts of the compound boss so
as to add to the propelling power of the screw.
By placing a single boss in the manner described at a sufficient angle to the
centre line of the shaft, the line of junction of a single blade may be made to pass
round or nearly round the axis of the shaft, the angle or pitch of the blade
remaining the same as in an ordinary screw.
Three or more blades may be used instead of two, the boss being composed of a
corresponding number of parts.

page_text: DELICATION.
I, WILLIAM HAMILTON KINDERSLEY BRADFORD, of Windsor, in the County
of Berks, and 35, Southampton Buildings, Chancery Lane, in the County of
Middlesex, formerly Major, 108th Regiment do hereby declare the nature of my
invention for "IMPROVEMENTS IN SCREW PROPELLORS" and in what manner the
same is to be performed, to be particularly described and ascertained in and
by the following statement and accompanying drawing (that is to say):—
My invention relates to screw propellors ordinarily used for propelling vessels,
and it has for its object a novel method of forming such propellors so that great
strength is obtained and their effective power is increased as compared with screw
propellora as ordinarily made, without any increase of the space occupied by them
in the direction of the length of the vessel.
The accompanying drawing is in illustration of my invention. In ordinary screw
propellors, as illustrated in figures 1 and 2, a cylindrical or other boss b is fitted
and fixed upon the driving shaft a, and the blades of the screw c, c¹, are formed or
fixed upon the boss b, their root or the part where they join the boss being at an
angle with the centre line of the shaft corresponding with the pitch of the screw
blades c, c¹.
In order to put my present invention in operation, supposing it to be applied to
an ordinary two bladed screw similar to that shewn in figures 1 and 2, I make a
double or compound boss separated by a plane passing through the axis of the
screw, and each part being fixed upon the shaft not parallel with the latter but at
an angle proportioned to the pitch of the screw, as illustrated in figure 3, which
shows one part 6 of the compound boss fixed upon the shaft a at an angle.
In figures 4 and 5 the other part b¹ of the compound boss is shewn fixed upon
the other side of the shaft a at an opposite angle to that of the part b.
A screw blade c, c, (of any desired shape, and occupying in end view a greater
or less segment as may be desired of the circle described by its outer edge during
its revolution,) is formed upon or attached to each part 6, 61, of the compound boss,
and by the method of arrangement described and shewn it will be seen that the
line of junction of the blade with the boss, whilst remaining at the same angle as
in ordinary screws as shewn in figures 1 and 2, such angle depending upon the
pitch of the screw, describes a larger segment of a circle round the circumference of
the boss and the axis of the shaft, such line of junction of each blade extending (in
the example illustrated in figures 4 and 5) round half of an entire circle, whilst it
may be made to extend round a still larger segment by properly proportioning the
angle of the boss and the pitch of the screw.
It is to be understood that the two parts b, 61, of the compound boss form one
single piece, and that the blades are opposite and alternate to each other, the
blade c passing round and being attached to the part 6 of the boss, and the blade ct
passing round and being attached to the other part b¹ of the boss, and each blade
occupying one half of a complete disc, in end view, or even more than half of such
a complete disc, or less than half (as shown in the drawing).

page_text: The parts of the compound boss b, 61, not required for the attachment of the
blades may be cut away and made of such shape as to reduce as much as possible
the resistance to its passage through the water, as illustrated in figure 6.
Additional supplementary blades may be formed or fixed upon other parts of the
compound boss so as to add to the 'propelling power of the screw.
By placing a single boss in the manner described at a sufficient angle to the
centre line of the shaft, the line of junction of the blade may be made to pass
round or nearly round the axis of the shaft, the angle or pitch of the blade
remaining the same as in an ordinary screw. By the novel method of construction
described, considerable additional propelling surface of the screw blades is obtained
without increasing their length, whilst their strength is increased.
It is evident that my invention may be applied to screws of three or four blades,
the shape of the compound boss being modified by forming it of a corresponding
number of parts.
I do not confine myself to the precise form and proportions of the propellor,
which may be varied to suit the circumstances in which it is to be applied; and it
may be made of any suitable material, but 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
The method of arranging the part of the boss to which the screw blade is
attached, at an angle to the driving shaft so that the line of junction extends round
a considerable segment of an entire circle, substantially as described and shewn in
the drawing.