IMPROVE- MENTS IN SCREW PROPELLERS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said William Tate at the Office
of the Commissioners of Patents on the 1st November 1882.
WILLIAM TATE of Sunderland in the County of Durham Engineer "IMPROVE-
MENTS IN SCREW PROPELLERS
"
The object of this invention is to construct propellers of steel or other metals,
with loose blades, bolted on to a boss or centre piece.
The boss (preferably of steel) is made with two or more arms (corresponding
with the number of blades intended to be used) radiating from the centre, and at
an angle due to the amount of "pitch" at that part, and of the same width as the
blades, of sufficient projection from the "boss" to allow bolts to be passed through.
To these arms the propeller blades are fixed with bolts and nuts, slots are also cast
in the "boss" into which the roots of the blades are stepped, and this, with or
without the addition of shoulders on the blades fitting the outer edges of the arms,
tends to relieve the bolts of part of the strain of the blades upon them..
The arms on the "boss" and the lower portions of the blades are stiffened with
ribs between which the bolts pass, and the spaces may be afterwards filled up with
cement thus protecting the nuts and bolt heads from corrosion and presenting a
smooth and uniform surface to the water.
"
By this mode of construction the blades can be made exceptionally thin, and
more uniform in thickness, and being without any large "fillets can be satis-
factorily annealed and rendered homogenous. The blades, or any one of them, can
be readily removed and replaced (without disturbing the "boss") even when the
vessel is afloat and spare blades can be carried stowed in a very small space.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, and of an
Order of the Lord Chancellor, filed by the said William Tate in the Great Seal
Patent Office on the 5th May 1883.
WILLIAM TATE of Sunderland in the County of Durham Engineer IMPROVE-
MENTS IN SCREW PROPELLERS
The object of this invention is to construct propellers of steel or other metals,
with loose blades, bolted on to a boss or centre piece.
The boss (preferably of steel) is made with two or more arms (corresponding
with the number of blades intended to be used) radiating from the centre, and at
an angle due to the amount of pitch" at that part, and of the same width as tho
blades, of sufficient projection from the "boss" to allow bolts to be passed through.
To these arms the propeller blades are fixed with bolts and nuts, slots are also cast
in the "boss" into which the roots of the blades are stepped, and this, with or
without the addition of shoulders on the blades fitting the outer edges of the arms,
tends to relieve the bolts of part of the strain of the blades upon them.
The arms on the "boss" and the lower portions of the blades are stiffened with
ribs between which the bolts pass, and the spaces may be afterwards filled up with
cement thus protecting the nuts and bolt heads from corrosion and presenting a
smooth and uniform surface to the water.
"By this mode of construction the blades can be made exceptionally thin, and
more uniform in thickness, and being without any large "fillets" can be satis-
factorily annealed and rendered homogenous. The blades, or-any-one-of-them, can
be readily removed and replaced (without disturbing the "boss") even when the
vessel is afloat and spare blades can be carried stowed in a very small space.
DESCRIPTION OF DRAWINGS.
On the accompanying sheet of drawings Figure 1. is a Section, on the fore and
aft line, of the boss and one blade of a right-hand propeller constructed according
to my invention the outline, of the blade- being also indicated. Figure 2 is a
developed plan of a blade and Figure 3 is a section through the root at A. B.
Figure 1, where bolted to the boss. The saine letters refer to similar parts on all
the Figures.
A is the boss having arms B cast upon it and slots or recesses C formed in it to
receive the roots of the blades D
The face of the arm B and the recess C, on the boss A, are both truly planed
and the face of the blade next arm B, also the root where stepped into recess, are
also planed. Upon the root of the blade ribs E E E are cast and also from the
boss to the arms E' E' E'. Between these ribs are bolts F F F F by means of
which, after the blade is fitted into the recess in boss, it is bolted to the boss
through the arm B, and the spaces between the ribs, and round the bolt heads and
nuts, may be filled up with cement or other suitable composition level with the top
of the ribs. The outer edge of the arm B as shewn, is formed with a bevilled
edge and a shoulder G on the blade is formed with a corresponding bevilled edge
so as to fit accurately upon each other and I have found this in practice to be of
great service in relieving the bolts and giving stability to the whole Screw especially
in going astern.
Having now described my invention and the manner in which I propose to carry
it into practical application I declare that what 1 claim as new and secured to me
by Letters Patent is―
In a Screw propeller, of metal such as cast steel, securing removable blades to the

page_text: boss by means of recesses therein, into which the roots of the blades are stepped; in
conjunction with arms cast with the boss and to which such blades are bolted and
preferably further secured by shoulders in the manner and for the purposes herein
above described with reference to and illustrated in the accompanying Sheet of
drawings.
.
In witness whereof I the said William Tate have hereunto set my hand and
seal this thirtieth day of April in the year of our Lord One thousand
eight hundred and eighty three