IMPROVEMENTS IN SCREW PROPELLERS
Year: 1879

page_text: LETTERS PATENT to Samuel Wilkinson Snowden, of 5, Waverley Terrace,
Kenilworth, Rathgar, Dublin, for the Invention of "IMPROVEMENTS IN SCREW
PROPELLERS."
Sealod the 27th July 1880, in pursuance of an Order of the Lord Chancellor, and
dated the 30th December 1879.
PROVISIONAL SPECIFICATION left by the said Samuel Wilkinson Snowden
at the Office of the Commissioners of Patents on the 30th December 1879.
SAMUEL WILKINSON SNOWDEN, of 5, Waverley Terrace, Kenilworth, Rathgar,
Dublin. "IMPROVEMENTS IN SCREW PROPELLERS." 事
This Invention has for its object improvements in screw propellers. I form the
boss on the propeller shaft in two parts, and in it conical recesses to receive the
stems of the screw blades. The stem is largest at the end where it most nearly
approaches the shaft, and the hole or recess in the boss into which the steni is
received is of corresponding form. The two parts of the boss are brought together
and are fixed upon the shaft embracing the stems of the screw blades, which are
thus securely held.
They are nevertheless able to turn, more or less, according as they may be
limited by stops provided for the purpose; the object being to permit the propeller
blades to find their own pitch automatically.
Or in place of forming a conical cavity in the boss the hole in the boss may be
parallel, the boss being then made in one piece. The parallel hole receives then a
bushing adapted to the conical stem of the propeller blade, and this bushing is kept
in its place by a shell surrounding the boss, and which is put on in two parts.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, and of
an Order of the Lord Chancellor, filed by the said Samuel Wilkinson Snowden
in the Great Seal Patent Office on the 28th July 1880.
SAMUEL WILKINSON SNOWDEN, of 5, Waverley Terrace, Kenilworth, Rathgar,
Dublin. "IMPROVEMENTS IN SCREW PROPELLERS."
This Invention has for its object improvements in screw propellors.
I form the boss on the propellor shaft in two parts, and in it conical recesses to
receive the stems of the screw blades. The stem is largest at the end where it
most nearly approaches the shaft, and the hole or recess in the boss into which the
stem is received is of corresponding form. The two parts of the boss are brought
together and are fixed upon the shaft embracing the stems of the screw blades,
which are thus securely held. They are nevertheless able to turn, more or less,
according as they may be limited by stops provided for the purposes, the object
being to permit the propellor blades to find their own pitch automatically.
Or in place of forming a conical cavity in the boss, the hole in the boss may be
parallel, the boss being then made in one piece. The parallel hole receives then a
bushing adapted to the conical stem of the propellor blade, and this bushing is kept
in its place by a shell surrounding the boss, and which is put on in two parts.
In order that my said Invention may be most fully understood and readily
carried into effect, I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a rear elevation of the screw propellor constructed according to my
Invention; in this Figure portions only of the blades of the propellor are shown;
Figure 2 is a rear elevation of the propellor complete, except that the after half of
the boss is removed and the shaft is in section; Figure 3 is a side elevation of the
propellor; two of the blades are in this Figure broken away; Figure 4 is a side
elevation of the propellor, but with the boss in section. a is the propellor shaft,
and 6', 6, are the two parts of which the boss is composed, they shut together,
and studs b* projecting from the face of the one part of the boss enter holes in the
other part; c, c, are the screw blades, they have tapered stems c', c', (as shown in
the Drawing there is a double taper), and these stems are shut between the two
parts b¹, b¹¹, of the boss which enclose cavities of corresponding form. The stems c¹
may advantageously be clothed with brass; this is represented by the double lines
in the Drawing. Above the stem of the blade and between it and the blade proper
there is in each case a flange or collar c¹¹, which abuts against the side of the boss.
By these means the blades are securely held to the shaft, but so that they are free
to turn. The angle through which the blades can turn is limited in each case by a
pin d screwed into the face of the boss in notches cut out from the collar c¹¹ of the
screw blade. The blades are thus when the propellor is in motion, free to set
themselves and to find for themselves the pitch at which to work.
The boss is keyed on to the shaft, and is further secured by a nut e screwed on
to the end of the shaft, and then fastened by a pin.
Figures 5, 6, 7, and 8 show another method for securing the propellor blades to
the shaft whilst leaving them free to turn and find their own pitch automatically.
Figure 5 is a back elevation; Figure 6 is also a back elevation, but with the boss
in section; Figure 7 is a side elevation, and Figure 8 also a side elevation, but
with the boss in section.
The boss b in this case is in one piece, and approximately globular. There are
cylindrical holes in the boss to receive the conical or tapered stems of the blades.
The space in each hole around the stem of the propellor blade is filled with a
corresponding bushing f; g², g¹¹, is a shell made in two parts and surrounding the
boss; the parts are bolted together by four bolts at the corners. This shell prevents
the bushing from escaping from the holes in the boss, and it may also (as the

page_text: Drawing represents) be made to embrace tapered projections upon the stems of the
propellor blades. The boss and the shell are secured to the screw shaft by a key,
and also by means of a nut e upon the end of the shaft.
Figures 9, 10, and 11 shew an arrangement according to which I mount the
screw blades, as already described, so that they are free to turn upon the boss
through a small angle, but in place of allowing them to find their positions
automatically, I set them to the positions desired from time to time by apparatus
from within the ship. Figure 9 is an elevation of the stern of the ship with the
propellor and gear complete, Figure 10 is a back elevation, and Figure 11 is a
sectional plan. The arrangement of the propellor is the same as has already been
described in respect to the Figures 1, 2, 3, and 4, but the flange or collar c" of each
propellor blade has an arc of teeth formed upon it with which a worm g engages.
The screw worms g, g, are carried in bearings formed upon the boss, and by turning
the worms the blades can be set to any desired angle of pitch. The worms are
tubular, and they receive spindles h, h. i is a key which can be worked from the
interior of the ship. By turning the propellor shaft each of the spindles / can in
turn be brought to the key. The key passes over the square head of the spindle,
and the key then carries the worm round with it whilst the blade is set to the
desired angle.
The spindles h, h, have an hexagon or octagon collar on them, which is intended
to prevent each blade shifting when the collar is in the recess made to receive it in
the forward half of the boss.
At the after end of each spindle india rubber washers or a solid piece of india
rubber fitted in a box or case made to receive it; between the point of the spindle
and the india rubber a plate is inserted. When the key is thrust on the spindle,
the hexagonal or octagon collar is pushed out of its recess as described, and then
the worm can be made to rotate by the key as required. When the thrust is
taken off the key the india rubber in the box or case pushes back the spindle, and
the hexagon or octagon collar goes back into the recess.
When it is required to apply the key i, it is thrust by the action of the screw
arrangement inside the ship (a screwed part on the key having a nut on it which
works between the jaws of a bracket, and is turned by a ratchet), a ratchet also
or wheel turns the key.
The whole of the moving or working gear can be cased over by a light casing of
metal
Having thus described the nature of my said Invention, and the manner of
performing the same, I would have it understood that I claim,—
First. My improvements in screw propellors, consisting in mounting the
propellor blades upon the boss in such manner that they can rotate through a
small angle, and automatically set themselves to the pitch at which they will
work.
Second. The construction of screw propellors, substantially as described and
shown by the Figures 1, 2, 3, and 4 of the annexed Drawings.
Third. The construction of screw propellors, substantially as described and
shown by the Figures 5, 6, 7, and 8 of the annexed Drawings.
Fourth. The combined arrangement described in respect to the Figures 9, 10, and
11 of the Drawings, admitting of the pitch of my propellor being controlled from
the interior of the ship.
In witness whereof, I, the said Samuel Wilkinson Snowden, have hereunto set
my hand and scal, this Twenty seventh day of July, in the year of our
Lord One thousand eight hundred and eighty.